  PUBLISHED AS A MEMENTO OF A SERIES OF LECTURES GIVEN BY THE AUTHOR |
PREFACE.
In the summer of 1892 while the Author was in California, preparing for a Lecturing tour through Australia and India, he received an invitation from the Fine Arts Commission of the World's Columbian Exposition to give a series of Lectures on Zoopraxography in association with the Exposition now being held in Chicago.
As these Lectures under the more familiar title of "The Science of Animal Locomotion in Its Relation to Design in Art" had already been given at nearly all the principal Institutions of Art, Science and Education in Europe and in the United States, (see appendix A) the Author was induced to believe that they might be repeated in a popular manner at the Exposition, with some appreciation of the importance of the facts which his investigation has revealed, not merely by the student of Nature or of Art, but by that large and important class of students, known as the general public.
Under this impression he delayed his far Occidental expedition and returned to Chicago to find a commodious theater erected for this special purpose on the grounds of the Exposition, to which the name of ZoÖpraxographical Hall had been given; the Science of ZoÖpraxography having had its origin in the Author's first experiments in 1872. It is not intended in this monograph to give more than a synopsis of the usual course of Lectures on the subject, nor to reproduce any of the pictured or sculptured representations which are necessary for its proper elucidation, but merely to describe the common methods of limb action adopted by quadrupeds—especially by the horse—in their various acts of progressive motion, and to illustrate the most important phases of these movements by tracings from the original photogravures of the Author's work.
In the presentation of a Lecture on ZoÖpraxography the course usually adopted is to project, much larger than the size of life upon a screen, a series of the most important phases of some act of animal motion—the stride of a horse, while galloping for example—which are analytically described. These successive phases are then combined in the ZoÖpraxiscope, which is set in motion, and a reproduction of the original movements of life is distinctly visible to the audience.
With this apparatus, horse-races are reproduced with such fidelity that the individual characteristics of the motion of every animal can readily be seen; flocks of birds fly across the screen with every movement of their wings clearly perceptible; two gladiators contend for victory with an energy which would cause the arena to resound with wild applause, athletes turn somersaults, and other actions by men, women and children, horses, dogs, cats and wild animals, such as running, dancing, jumping, trotting and kicking, are illustrated in the same manner. By this method of analysis and synthesis the eye is taught how to observe and to distinguish the differences between a true and a false impression of animal movements. The ZoÖpraxiscopical exhibition is followed by illuminated copies of paintings and sculptures, demonstrating how the movement has been interpreted by the Artists of all ages; from the primitive engravers of the cave dwelling period, to the most eminent painters and sculptors of the present day.
INTRODUCTION.
In the year 1872, while the Author was engaged in his official duties as Photographer of the United States Government for the Pacific coast, there arose in the city of San Francisco one of those controversies upon Animal Locomotion, which has engaged the attention of mankind from the dawn of symbolical design, to the present era of reformation in the artistic expression of animal movements.
The subject of this particular dispute was the possibility of a horse having all of his feet free of contact with the ground at the same instant, while trotting, even at a high rate of speed, and the disputants were Mr. Frederick MacCrellish and the Hon. Leland Stanford.
The attention of the Author was directed to this controversy and he immediately sought the means for its settlement.
At this time the rapid dry plate had not yet been evolved from the laboratory of the chemist, and the problem before him was to develop a sufficiently intense and contrasted image upon a wet collodion plate, after an exposure of so brief a duration that a horse's foot moving with a velocity of more than a hundred lineal feet in a second of time, should be photographed practically "sharp."
A few days' experimenting and about a dozen negatives, with a celebrated fast trotter—"Occident"—as a model, while trotting at the rate of a mile in two minutes and sixteen seconds, laterally in front of the camera, decided the argument for once and for all time in favor of those disputants who held the opinion that a horse while trotting was for a portion of his stride entirely free from contact with the ground. With a knowledge of the fact that some horses while trotting will make a stride of twenty feet or more in length, it is difficult to understand why there should ever have been any difference of opinion on the subject.
These first experiments of ZoÖpraxography were made at Sacramento, California, in May, 1872. A few impressions were printed from the selected negative for private distribution, and were commented upon by the "Alta California," a newspaper published in San Francisco.
Thus far the photographs had been made with a single camera, requiring a separate trotting for each exposure. The horse being of a dark color and the background white, the pictures were little better than silhouettes, and it was difficult to distinguish, except by inference, the right feet from the left.
Several phases of as many different movements had been photographed, which the Author endeavored with little success to arrange in consecutive order for the construction of a complete stride.
It then occurred to him that if a number of cameras were placed in a line, and exposures effected successively in each, with regulated intervals of time or of distance, an analysis of one single step or stride could be obtained which would be of value both to the Scientist and the Artist.
The practical application of this system of photographing required considerable time for its development, and much experimenting with chemicals and apparatus.
It being desirable that the horses used as models should be representatives of their various breeds, and the Author not being the owner of any that could be fairly classed as such, obtained the coÖperation of Mr. Stanford, who owned a fine stud of horses at his farm at Palo Alto, and there continued his labors.
The apparatus used at this stage of the investigation was essentially the same as that subsequently constructed for the University of Pennsylvania, the arrangement of which will be described further on.
Some of the results of these early experiments which illustrated successive phases of the action of horses while walking, trotting, galloping, &c., were published in 1878, with the title of "The Horse in Motion." Copies of these photographs were deposited the same year in the Library of Congress at Washington, and some of them found their way to Berlin, London, Paris, Vienna, &c., where they were criticized by the journals of the day.
In 1882 the Author visited Europe and at a reception given him by Monsieur Meissonier was invited by that great painter to exhibit the results of his labors to his brother Artists who had assembled in his studios for that purpose. M. Meissonier was the first among Artists to acknowledge the value to Art design of the Author's researches; and upon this occasion, alluding to a full knowledge of the details of a subject being necessary for its truthful and satisfactory translation by the Artist, he declared how much his own impression of a horse's motion had been changed after a careful study of its consecutive phases.
It is scarcely necessary to point out, in confirmation of M. Meissonier's assertions, the modifications in the expression of animal movements now progressing in the works of the Painter and the Sculptor, or to the fact of their being the result of studious attention to the science of ZoÖpraxography.
In the same year, during a lecture on "The Science of Animal Locomotion in Its Relation to Design in Art," given at the Royal Institution (see Proceedings of the Royal Institution of Great Britain, March 13, 1882), the author exhibited the results of his experiments at Palo Alto, when he, with the ZoÖpraxiscope and an oxy-hydrogen lantern, projected on the wall a synthesis of many of the actions he had photographed.
It may not be considered irrelevant if he repeats what he on that occasion said in his analysis of the quadrupedal walk:—
"So far as the camera has revealed, these successive foot fallings are invariable, and are probably common to all quadrupeds....
"It is also probable that these photographic investigations—which were executed with wet collodion plates, with exposures not exceeding in some instances the one five-thousandth part of a second—will dispel many popular illusions as to the gaits of a horse, and future and more exhaustive experiments, with the advantages of recent chemical discoveries, will completely unveil all the visible muscular action of men and animals even during their most rapid movements....
"The employment of automatic apparatus for the purpose of obtaining a regulated succession of photographic exposures is too recent for it to be generally used for scientific experiment or for its advantages to be properly appreciated. At some future time the philosopher will find it indispensable for many of his investigations."
The great interest manifested in the results of his preliminary labors convinced the Author that a comprehensive and systematic investigation with improved mechanical appliances, and newly-discovered chemical manipulations, would demonstrate many novel facts, not only interesting to the casual observer, but of indisputable value to the Artist and to the Scientist. This investigation and the subsequent publication in the elaborate manner determined upon, assumed such imposing proportions, and necessarily demanded so large an expenditure, that all publishers, not unnaturally, shrank from entering the unexplored field.
In this emergency, through the influence of its Provost, Dr. William Pepper, the University of Pennsylvania with an enlightened exercise of its functions as a contributor to human knowledge, instructed the Author to make, under its auspices, a comprehensive investigation of "Animal Locomotion" in the broadest significance of the words, (see appendix B) and some of the Trustees and friends of the University constituted themselves a committee for the purpose of promoting the execution of the work. These gentlemen were Dr. William Pepper, Chas. C. Harrison, J. B. Lippincott, Edw. H. Coates, Samuel Dickson and Thomas Hockley.
The Author acknowledges his obligations to these gentlemen for the interest they took in his labors; for without their generous assistance the work would probably never have been completed; the total amount expended—nearly forty thousand dollars—being entirely beyond his own resources. To Drs. F. X. Dercum, Geo. F. Barker and Horace Jayne, of the University, the Author is also indebted for much valuable assistance.
STUDIO, APPARATUS, AND METHOD OF WORKING.
For a proper appreciation of the care taken in the Investigation of Animal Locomotion at the University of Pennsylvania to ensure accurate record of the consecutive phases of the various movements, attention to the system adopted is necessary.
In the diagram, B is the Lateral background; consisting of a shed 37 metres or about 120 feet, long, the front of which is open, and divided by vertical and horizontal threads into spaces 5 centimetres, or about 2 inches, square, and by broader threads into larger spaces 50 centimetres, or about 19¾ inches, square.
At C and C, 37 metres, or about 120 feet, apart are "fixed" backgrounds, with vertical threads 5 centimetres, or about two inches, from their centres, with broader threads 30 centimetres, or about 12 inches, from their centres.
For some investigations, readily distinguishable in the plates, "portable" backgrounds are used, consisting of frames 3 metres wide by 4 metres high,—about 10 feet by 13 feet 4 inches,—over some of which black cloth and over others white cloth is stretched, all being divided by vertical and horizontal lines into square spaces of the same description as those of the lateral background.
These portable backgrounds are used when photographing birds and horses, and also wild animals when possible to do so.
L. A lateral battery of 24 automatic electro-photographic cameras, arranged parallel with the line of progressive motion, and usually placed therefrom about 15 metres or 49 feet.
Slow movements are usually photographed with lenses of 3 inches diameter and 15 inches equivalent focus; the centres of the lenses being 15 centimetres, or about 6 inches, apart.
Rapid movements are usually photographed with a portable battery of cameras and smaller lenses.
The centre, between lenses 6 and 7, is opposite the centre of the track T.
For illustrations comprising both "Laterals" and "Foreshortenings," cameras 1 to 12 only are used.
When "Laterals" alone are required, cameras 13 to 24 are connected with the system and used in their regular sequence.
R. A portable battery of 12 automatic electro-photographic cameras, the lenses of which are 1¼ inches diameter and 5 inches equivalent focus; the lenses are arranged 7½ centimetres, or about 3 inches, from their centres. When the battery is used vertically, lens 6 is usually on the same horizontal plane as the lenses of the lateral battery.
In the diagram this battery is arranged vertically for a series of "Rear Foreshortenings," the points of view being at an angle of 90 degrees from the lateral battery.
F. A battery of 12 automatic electro-photographic cameras, similar to that placed at R, arranged horizontally for "Front Foreshortenings," the points of view averaging an angle of 60 degrees from the lateral battery.
O. The position of the operator; the electric batteries; the chronograph for recording the intervals of time between each successive exposure; the motor for completing the successive electric circuits, and other apparatus connected with the investigation.
T T. The track parallel with the lateral battery and covered with corrugated rubber flooring.
M. The model, approaching the point number "1" on the track where the series of photographic illustrations will commence.
An estimate having been made of the interval of time which will be required, between each photographic exposure, to illustrate the complete movement, or that portion of the complete movement desired, the apparatus is adjusted to complete a succession of electric circuits at each required interval of time, and the motor is set in operation. When the series is to illustrate progressive motion; upon the arrival of the model at the point marked "1" on the track, the operator, by pressing a button, completes an electric circuit, which immediately throws into gearing a portion of the apparatus hitherto at rest. By means of suitably arranged connections, an electric current is transmitted to each of the 3 cameras marked "1" in the various batteries, and an exposure is simultaneously made on each of the photographic plates, respectively, contained therein. At the end of the predetermined interval of time, a similar current is transmitted to each of the cameras marked "2," and another exposure made on each of the 3 next plates, and so forth until each series of exposures in each of the three batteries is completed. Assuming the operator to have exercised good judgment in regulating the speed of the apparatus, and in making the first electric contact at the proper time, and that the figures 1 to 12 represent the distance traversed by the model in executing the movement desired, the first three photographic exposures—that is, one exposure in each battery—will have been synchronously made when the model was passing the position marked "1" on the track T; the second three exposures will have been made when the model was passing the position marked "2," and so on until twelve successive exposures were simultaneously made in each of the three batteries. This perfect uniformity of time, speed, and distance, however, was not always obtained.
When this monograph was commenced it was not intended by the author to give any more than a general idea of the method adopted for obtaining the results of his investigation; it has, however, been considered that a few illustrations and brief description of the apparatus devised and used by him may not be without interest to other students.
For the use of these illustrations he is indebted to the courtesy of Rev. Jesse Y. Burk, the Secretary of the University, and to J. B. Lippincott Company, the publishers of "The Muybridge Work at the University of Pennsylvania," a book which contains, among other essays upon the subject, "Materials for a Memoir on Animal Locomotion, by Harrison Allen, M. D.," and "A Study of Some Normal and Abnormal Movements, by Francis X. Dercum, M.D., Ph.D."
Figure 1 is a view of the building containing the lateral battery of twenty-four photographic cameras, all of which were used when as many consecutive phases of an act of motion were required.
Immediately in front of each of these cameras, and detached therefrom, was placed an electro-photographic exposor, a side section of which is represented by Figure 2, in which A is a continuous band of thin rubber cloth impervious to light; the edges of which are bound with strong tape, and arranged to run in a groove, and over two rollers RR which are attached to a frame.
In this endless band are two apertures OO of suitable size, and so arranged that their full openings as they pass each other shall simultaneously take place in front of the center of the lens L.
The upper and lower edges of these apertures are kept taut by light steel rods attached to the tape binding.
To the lower rod of the front aperture is fastened a ring C and a cleat, to which some elastic rubber bands B are attached; these bands are easily removable and their number increased at discretion; in some instances of rapid exposures a tension of twenty-five pounds or more was required. On a shelf of the frame is a magnet M, over the top of which is arranged a steel lever G pivoted near the end D which terminates with a slightly indented projection.
The armature of the magnet is pivoted at H; its upper arm terminates with a shoulder I. S is a spring to prevent the accidental shifting of the shoulder from its contact with the lever when the exposor is ready for its function. N is a set screw to adjust the distance of the armature from the magnet. To prepare for a series of photographic exposures—the plates having been already placed in the cameras—the end of the lever G is placed under the shoulder I; the endless curtain is revolved until the front aperture O is raised to its proper position, when the ring C is hooked upon the projecting point D. A cord attached to the rubber bands B is drawn around the pulley P, and a ring at its end is slipped over a pin, which keeps the spring at a proper state of tension. Upon the completion of an electric circuit the armature is drawn towards the magnet; the end of the lever is released from its contact with the shoulder; the ring C is released from the projecting point D; the front of the endless curtain is drawn rapidly downward; the apertures meet in the center of the lens, form a gradually expanding and then contracting diaphragm, and the exposure is made. A front view of three electro-photographic exposors is seen in Figure 3. The first of these represents the exposor set and ready for an exposure; the second shows the meeting of the apertures at the commencement of an exposure; the third, their position near the completion of the exposure, they having in the meanwhile uncovered the lens to their full capacity.
Figure 4 illustrates a portable battery of twelve electro-photographic exposors; it consists of a rectangular box divided into compartments, open at the front and rear.
In twelve of these compartments are arranged rollers, curtains, magnets, etc., as previously described, and a compartment through which a focusing lens is used. The two end compartments provide for the adjustment of the camera, which is supported in the box to the rear of the exposing arrangements. A cable of insulated wires for connecting the twelve magnets with the exposing motor, contains a wire for the return current. As seen in the engraving, seven of the magnets by the passage of their respective currents have completed their releasing operations. In the eighth compartment the two apertures in the exposing band are in the act of effecting an exposure. The remaining four magnets are awaiting their turn for action.
Figure 5 is a photographic camera divided into thirteen compartments, each having a lens of the same construction, and the same focal length; these are arranged to correspond with the compartments in the electro-exposors.
One of the lenses is provided with a focusing screen, and with it the other twelve lenses are adjusted to a proper focus without removing the plate holder behind them from its position in the camera.
The plate holder is constructed to hold three dry plates, each three inches by twelve inches; the front is divided into twelve compartments, each three inches square.
Light is excluded from the front by a roller blind, strengthened by thin narrow slats of hard wood; the blind works in grooves, is drawn over a concealed roller, and covers the back of the holder when the plates are being exposed.
Figure 6 is a rear and side view of the circuit maker, conventionally called the exposing motor.
The motive power is an adjustable weight attached to a cord which is wound around a drum. Twenty-four binding posts are attached to the table at the back of the exposing motor; other binding posts are arranged for return or other currents.
Figure 7 illustrates a front and side view of the upper part of the exposing motor. Fastened to the frame is a ring of hard rubber, in which are inserted twenty-four insulated segments of platinum-coated brass; these segments are connected by insulated wires to the twenty-four binding posts on the back of the motor table, figure 6.
A shaft, connected by an arrangement of geared wheels to the drum, passes through the center of the segmented ring and carries a loose collar; a stout metal rod is firmly attached near its longitudinal center to this loose collar. One arm of the rod carries a laminated metal scraper, or contact brush, arranged to travel around the periphery of the ring, and in its revolution to make contact with each segment in succession. The contact brush is connected through the arm with one pole of the battery; and each segment—through its independent wire and magnet of the electro-exposors—with the other pole.
When twenty-four consecutive phases of an act of motion are to be photographed from one point of view, all of the insulated segments in the ring are put in circuit. When twelve consecutive phases are to be photographed synchronously from each of three points of view, each alternate segment is placed in circuit with the electric battery.
The manner in which the series of synchronous exposures is effected will be readily understood by reference to the diagram, 8.
All being in readiness, and the weights and fan wheel adjusted to cause the contact brush to sweep over the periphery of the ring at the required rate of speed, the drum, and with it the shaft is set in motion.
At the proper time, pressure on a button completes an independent circuit through the magnet seen below the segmented ring, figure 7, and in the side diagram of figure 8.
The action of the armature releases the lower end of the rod on the loose collar, which, by means of a coiled spring, is immediately thrown into gearing with the already revolving shaft; the contact brush sweeps around the segmented ring and effects the consecutive series of exposures at the pre-arranged intervals of time.
At the University the intervals varied from the one-sixtieth part of a second to several seconds.
A record of these time intervals was kept by a chronograph, a well known instrument; it comprises a revolving drum carrying a cylinder of smoke-blackened paper, on which, by means of successive electric contacts, a pencil is caused to record the vibrations of a tuning fork, while a second pencil marks the commencement of each photographic exposure. The number of vibrations occurring between any two successive exposures marks the time. The tuning fork used made one hundred single vibrations in a second of time. To ensure greater minuteness and accuracy in the record, the vibrations were divided into tenths, and the intervals calculated in thousandths of a second.
For the purpose of determining the synchronous action of the electro-exposors while making a double series of exposures, the accuracy of the time intervals as recorded by the chronograph, and the duration of the shortest photographic exposures used in the investigation, the two batteries of portable cameras were placed side by side, and the exposors were each connected with the exposing motor by separate lengths of a hundred feet of cable. The two series of cameras were pointed to a rapidly revolving disc of five feet diameter. The surface of the disc was black, with narrow white lines radiating from the center to the edge like the spokes of a wheel. A microscopic examination of the two series of resulting negatives proved that no variation could be discovered in the synchronous action of ten of the duplicated series of exposures, and that in the remaining two a variation existed in the simultaneity of a few ten-thousandths of a second—a result sufficiently near to simultaneity for all ordinary photographic work.
A reproduction of the chronographic record of one of these experiments is seen in figure 9.
The first line records the revolution of the disc; the second the vibration of the tuning fork; and each group of three long double markings in the third line indicates a photographic exposure.
The shortest exposures made at the University were—approximately—the one six-thousandth part of a second; such brief exposures are however for this class of investigation very rarely needed.
Some horses galloping at full speed will, for a short distance, cover about fifty-six or fifty-eight feet of ground in a second of time; a full mile averaging perhaps a hundred seconds. At this speed, a foot recovering its loss of motion will be thrust forward with an occasional velocity of at least 120 lineal feet in a second of time.
During the one one-thousandth part of a second the body of the horse will at this rate move forward about seven one-tenths of an inch, and a moving foot perhaps one and a half inches, not a very serious matter for the usual requirements of the amateur photographer.
A knowledge of the duration of the exposures, however, was in this investigation of no value, and scarcely a matter of curiosity, the aim always being to give as long an exposure as the rapidity of the action would permit, with a due regard to the necessary sharpness of outline, and essential distinctness of detail.
The power used for operating the magnets, through the exposing motor, was given from a lÉ ClanchÉ battery of fifty-four cells, arranged in multiple arc of three series, each of eighteen cells.
During the investigation at the University of Pennsylvania, more than a hundred thousand photographic exposures were made.
The negative plates were supplied by the Cramer Dry Plate Company of St. Louis, and the positive plates by the Carbutt Company of Philadelphia. On a favorable day five hundred or six hundred negatives were sometimes exposed; on one day the number of exposures reached seven hundred and fifty.
The electrical manipulations were directed by Lino F. Rondinella; the development room was in charge of Henry Bell. The author takes pleasure in acknowledging the skill, patience and energy which these gentlemen exhibited in their respective fields of labor.
Although the one six-thousandth part of a second was the duration of the most rapid exposure made in this investigation, it is by no means the limit of mechanically effected photographic exposures, nor does the one-sixtieth part of a second approach the limit of time intervals. Marey, in his remarkable physiological investigations, has recently made successive exposures with far less intervals of time; and the author has devised, and when a relaxation of the demands upon his time permit, will use an apparatus which will photograph twenty consecutive phases of a single vibration of the wing of an insect; even assuming as correct a quotation from Nicholson's Journal by Pettigrew in his work on Animal Locomotion that a common house fly will make during flight seven hundred and fifty vibrations of its wings in a second of time, a number probably far in excess of the reality.
The ingenious gentlemen who are persistently endeavoring to overcome the obstacles in the construction of an apparatus for aerial navigation, will perhaps some day be awakened by the fact that the only successful method of propulsion will be found in the action of the wing of an insect.
We will now resume the subject proper of this monograph.
It is impossible within its limits to trace the history of the art of delineating animals in motion, or to illustrate it with examples of the truthful impressions of the primitive Artists, or of the imaginative and erroneous conceptions of many of those of modern times. Certain phases of the facts of Animal Locomotion will alone be treated upon, as demonstrated by photographic research.
The illustrations and condensed definitions of the various gaits were prepared by the Author for the "Standard Dictionary." Before studying these it is essential that the meaning of the terms step and stride should be distinctly understood.
A STEP is an act of progressive animal motion, in which one of the supporting members of the body is thrust in the direction of the motion and the support transferred, wholly, or in part, from one member to another.
A STRIDE is an act of progressive animal motion, which, for its completion, requires all of the supporting members of the body, in the exercise of their proper functions, to be consecutively and regularly thrust in the direction of the movement until they hold the same relative positions in respect to each other as they did at the commencement of the notation. In the bipedal walk or run a step is one-half of a stride or full round movement. With all quadrupeds, except the kangaroo and other jumpers, four steps are necessary to complete the stride.
THE WALK.
The WALK is a method of progressive motion with a regular individual succession of limb movements. In the evolution of the terrestrial vertebrates the walk was probably the first adopted method of locomotion, and its execution is regulated by the law that the movement of the superior limb precedes the movement of its lateral inferior limb. This is proved not merely by the ordinary quadrupedal walk, but by the suspended motion of the sloth; the crawling of the child upon the ground, the erect walk of man; and the inverse limb movements of the ape tribe.
The relative time intervals of the foot-fallings vary greatly with many species of animals, and even with the same animal under different conditions.
Selecting the horse for the purpose of illustration we find that during the walk—his slowest progressive movement—he has always two, and for a varying period of time, or distance, three feet on the ground at once, while during a very slow walk the support will devolve alternately upon three feet and upon four feet.
If the notation of the foot-fallings commences with the landing of the right hind foot, the order in which the other feet are placed upon the ground will be: the right fore, the left hind, and the left fore, commencing again with the right hind.
Assuming that our observation of the stride of a horse during an ordinary walk commences with the landing of the right hind foot, the body will then be supported by both hind and the left fore feet. The left hind is now lifted, the support of the body devolves upon the diagonals—the right hind and left fore—and continues so supported until the left hind is in the act of passing to the front of the right; when the right fore is next placed on the ground. The left fore is now raised, and the body is supported by the right laterals, until the landing of the left hind foot relieves its fellow hind of a portion of its weight. Two steps or one-half of a stride have now been made, and with the substitution of the right feet for the left, two other steps will be executed in practically the same manner, and a full stride will have been completed. We thus see that during the walk a quadruped is supported by eight different methods, the supporting limbs being consecutively:
Both hind and left fore.
Right hind and left fore diagonals.
Right hind and both fore.
Right hind and right fore laterals.
Both hind and right fore.
Left hind and right fore diagonals.
Left hind and both fore.
Left hind and left fore laterals.
Followed as at the commencement with both hind and left fore.
When, therefore, during a walk, a horse is supported on two legs, with two feet suspended between them, each pair are laterals. On the other hand, when the suspended feet are respectively in advance of, and behind the supporting legs, each pair are diagonals.
These invariable rules have been unknown or ignored by many distinguished artists of modern times.
THE AMBLE.
The amble is a method of progressive motion with the same sequence of foot fallings as the walk, but in which a hind foot or a fore foot is lifted from the ground in advance of its fellow hind foot or its fellow fore foot being placed thereon. The support of the body therefore devolves alternately upon a single foot and upon two feet; the single foot being alternately a hind foot and a fore foot, and the two feet being alternately laterals and diagonals. At no time is the body entirely unsupported.
The following series of illustrations will clearly demonstrate the consecutive foot fallings and some characteristic phases of an ambling stride:
The amble has various local names, such as the "single foot," the "fox trot," etc. It has sometimes been erroneously confused with the rack or the so-called "pace;" it is the most gentle and agreeable to the rider of all methods of locomotion of the horse, while the rack is the most ungraceful and disagreeable.
In Scott's romances are many allusions to the "ambling palfry." Ben Jonson in "Every Man in His Humor" speaks of going "out of the old hackney-pace to a fine, easy amble," and Dickens in "Barnaby Rudge" refers to "the gray mare breaking from her sober amble into a gentle trot."
The ambling gait is natural to the elephant, and to the horse, the mule and the ass; but in many countries these latter animals are not encouraged in its use.
THE TROT.
The trot is a more or less rapid progressive motion of a quadruped in which the diagonal limbs act nearly simultaneously in being alternately lifted from and placed on the ground, and in which the body of the animal is entirely unsupported twice during each stride.
Selecting for the purpose of illustration the phases occurring during two steps or one-half of a stride of 18 feet in length by a horse trotting at the rate of a mile in two minutes and twelve seconds, we find that at the instant his right fore foot strikes the ground, the left hind foot is a few inches behind the point where it will presently strike. As the feet approach the ground, the right hind leg is drawn forward with the pastern nearly horizontal, while the left fore leg is flexed under the body. After the feet strike the ground and the legs approach a vertical position the pasterns are gradually lowered, and act as springs to break the force of the concussion until they are sometimes bent to a right angle with the legs.
At this period the fore foot is raised so high as to frequently strike the elbow, while the diagonal hind foot is comparatively but little above the ground, and is about to pass to the front of the left hind.
The pasterns gradually rise as the legs pass the vertical until the right fore foot has left the ground and the last propelling force is being exercised by the left hind foot; which accomplished, the animal is in mid air.
The right hind foot continues its onward motion until it is sometimes much in advance of its lateral fore foot, the former, however, being gradually lowered, while the latter is being raised. The right hind and both fore legs are now much flexed, while the left hind is stretched backwards to its greatest extent with the bottom of the foot turned upwards, the left fore leg is being thrust forwards and gradually straightened, with the toe raised as the foot approaches the ground; which accomplished, with a substitution of the left limbs for the right, we find them in the same relative positions as when we commenced our examination, and one-half of the stride is completed.