THE ENGLISH AND FRENCH CHEMISTS CONTRIBUTE THEIR SHARE TOWARD THE ADVANCE OF MEDICAL KNOWLEDGE

During the latter part of the eighteenth century the chemists of England and France manifested a new and decidedly stronger interest in their branch of natural science; indeed, they seemed to have suddenly appreciated the fact that observation and experience afforded the only route by which they might secure a genuine and useful increase of their stock of knowledge. In the departments of physiology and pathology, for example,—not to mention also that of therapeutics,—there were at that period many questions which still remained unsettled and which could not be satisfactorily answered until a further advance had been made in the existing knowledge of chemistry. Hence the great importance of the movement to which I have just referred. To cite only one of these unsettled questions I will mention here that relating to the nature of the change which occurs in the blood when it loses its venous hue after passing through the lungs, and also, vice versa, when it loses its arterial color after passing through the tissues in other parts of the body. Harvey’s discovery had gone no further than to reveal the pathway of the blood in its winding course throughout the body, but now physiology demanded an explanation of the changes which this fluid undergoes in its travels along that pathway. The answer to this last question, as will now be shown, was not gained through the efforts of a single individual but by the researches that were made by several very able English and French scientists, more particularly by Joseph Priestley, the English chemist, and by Lavoisier, the French biologist and chemist. During the preceding fifty or sixty years the physicians of Europe had been obliged, for want of a more satisfactory explanation, to accept Stahl’s phlogiston theory (that all combustible materials contain an element to which he applied the name of “phlogiston”), at least as a basis or starting-point for the desired explanation.

Joseph Priestley, who was born at Fieldhead, near Leeds, England, in 1733, received his early education at a Dissenting school; and in 1755 he became a Dissenting minister at Needham Market. So far as the available evidence affords any clear indication of Priestley’s bent of character the inference is permissible that he was first and chiefly a scientist, but yet possessing a profoundly religious type of mind which the influences surrounding his boyhood doubtless helped to intensify. Thus, during his ministerial work he managed to devote a large part of his time to original investigations in the domain of chemistry; and, as early as in the year 1774, he succeeded in obtaining a gaseous product to which he gave the name of “dephlogisticated air.”^[16] A detailed description of this discovery of oxygen—the name which was given to the new gas at a later date—will be found in Vol. 2 of the second edition of Priestley’s “Experiments and Observations on Different Kinds of Air,” London, 1784. Broadly speaking, Priestley obtained the new product by heating the red oxide of mercury. Subsequently he discovered that respiration took place more easily, and that combustion progressed more actively, in the presence of this gas. But it is to the French chemist Lavoisier that we owe the knowledge of the full significance of oxygen. On the other hand, it was the English chemist Cavendish who confirmed Priestley’s discovery that atmospheric air is composed of water and different acids. Lavoisier, it is claimed, discovered that all the acids which he examined contain oxygen.

Speaking, at a later date, of his attempt to produce a work on the chemistry of the air, Priestley says: “I find it absolutely impossible to produce such a work that shall be anything like complete. My first publication I acknowledged to be very imperfect, and the present, I am as ready to acknowledge, is still more so. But, paradoxical as it may seem, this will ever be the case in the progress of natural science, so long as the works of God are, like himself, infinite and inexhaustible. In completing one discovery we never fail to get an imperfect knowledge of others, of which we could have no idea before; so that we cannot solve one doubt without creating several new ones. Travelling on this ground resembles Pope’s description of travelling among the Alps, with this difference, that here there is not only a succession, but an increase of new objects and new difficulties.”

Here is the description to which Priestley refers:—

On the 14th of July, 1791, there occurred a serious riot at Birmingham, where Priestley was at that time settled as a Dissenting minister. On that day a banquet was being given in honor of the French Revolution, those who organized this feast being in large measure Episcopalians. There were numerous fraudulent cards of invitation which, rumor said, were issued by Priestley. On the occasion itself numerous toasts were offered in which sentiments antagonistic to those generally entertained by the originators of the feast, were expressed. As the festival progressed the crowd became more and more excited and everybody seemed to be imbued with the idea that in some way or other Priestley was mixed up in the matter. The truth was, however, he had nothing whatever to do with it, was not present at the banquet, and even did not know that such a feast was being given. Nevertheless, the crowd would not listen to reason, and insisted that Priestley was the cause of the whole trouble. Accordingly they secured lighted torches and hastened to Priestley’s house which was located about half a mile from the city limits, and proceeded to set it on fire. Thus were destroyed, in the course of a few minutes, all his books, all his valuable scientific apparatus, all the registers of experiments covering a period of eleven years of unremitting toil. Priestley, who was then nearly seventy years old, lost practically everything that he possessed. For three days the rioting continued, many of the houses of Priestley’s friends being also destroyed by fire. Even the daily newspapers asserted that among Priestley’s papers were found evidences showing that a great conspiracy existed,—but for what evil purpose it was not stated. Insults of all sorts were heaped upon the innocent man, until finally he was compelled, by the situation of affairs in Birmingham, to leave the country. Fortunately for him, Priestley’s brother-in-law left him in his will the sum of £10,000 and also an annuity of £200. Thus provided for, Priestley left England in 1794 and settled in Pennsylvania. His death occurred in 1804.

Antoine Laurent Lavoisier was born in 1743 at Paris, and at an early age displayed a fondness for serious scientific studies. In 1768, although he had attained only his twenty-fifth year, he was chosen a member of the French Academy of the Sciences; and a very short time afterward he received the appointment of Fermier GÉnÉral (Government Collector of Taxes), an appointment which showed how highly he was esteemed for his ability as well as for his integrity. At first, Lavoisier, like nearly all his contemporaries, accepted Stahl’s phlogiston doctrine and his views with regard to animism (see pp. 432 and 433 of my work entitled: “The Growth of Medicine”); but gradually he entertained more and more serious doubts with regard to their correctness, and finally he came out boldly as an opponent of these doctrines. The experiments which he himself made, as well as those which were carried out by other scientists of the same period, forced him to conclude that, in all chemical processes, no such thing as an actual creation of something new takes place, nor is anything ever lost. This truth, he claimed, applies as well to living beings as to inanimate objects. In the middle of the eighteenth century the treatises on chemistry did not acknowledge this teaching as true. Vauquelin, for example, pointed to what he believed to be a fact, viz., that animals actually produce lime, inasmuch as hens—so he claimed—produce more lime than they ingest with their food. Lavoisier’s remarkable experiments showed that Stahl’s doctrine of animism, as well as the phlogiston theory, was untenable. Stahl maintained, for example, that there exists in all combustible bodies a special element which is set free during the combustion of such bodies, and to this element—as I have already stated on a previous page—he gave the name of “phlogiston.” Lavoisier, on the other hand, made it clear that combustion represents simply the combination of the two elements, carbon and oxygen; and at the same time he showed that the act of respiration in animals is a species of combustion, in the course of which oxygen combines with certain elements of the body to form water and carbonic acid. He did not, however, rest satisfied with these results, but—aided by Seguin—pushed his experiments to the point where he demonstrated the quantities of gas expired both by man and by animals; thus greatly increasing our knowledge of the phenomena of life.

Furthermore, Lavoisier was also the discoverer of a method of analysis (still employed to-day) by means of which it is possible to demonstrate the important fact that all organic bodies are composed of carbon, hydrogen and oxygen, sometimes in association with azote (lifeless matter). In a word, he brought physiological chemistry to such a stage of perfection that his successors have been able only to make additions to the facts which he discovered, but not to alter them in any essential respect.

Lavoisier’s mind seemed always preoccupied with questions relating to the grandeur and progress of humanity in its entirety. Here is a single example of the truth of this statement:—

When he learned from his own observations that the exhalation of carbonic acid increased during physical work, he drew the conclusion that men who are obliged to perform severe labor stand in need of a more abundant nourishment than is required by ordinary workmen in order to recover the carbon which had been expended in their severe labors; and he immediately urged that an effort be made to furnish the working class with better nourishment. The public functionary—he wrote at the end of his treatise on respiration (published in 1789)—is not the only individual who works for his country. The man of science, he added, is also fulfilling his patriotic duty when he teaches, by his investigations, how the misery which exists in the world may be alleviated. And if he accomplishes nothing more than to add a few years, or even only a few days, to the average duration of the life of man, he still may with justice claim the right to be given the glorious title of “benefactor of humanity.” (J. Rosenthal.)

France, at the time when Lavoisier wrote his treatise on respiration, was in the throes of a great revolution, out of which came the Republic. But this republic showed no gratitude to Lavoisier for the services which he had rendered to his country; for, on the 8th of May, 1794, it executed him without any specific charge having been brought against him, simply because he had held the hated office of Government Collector of Taxes. When one of Lavoisier’s personal friends, just before the prisoner was removed to the guillotine, called the judge’s attention to his scientific merits, this functionary replied: “We no longer have any use for men of science.”

Before closing this necessarily brief and somewhat superficial account of the work accomplished by the great French chemist, Lavoisier, I must beg permission to refer very briefly to the views which he entertained on the subject of heat-production. The chief significance of these studies of the fundamental phenomena of animal life is this: they afforded for the first time a solid basis for the theory of heat-production in living animals. This theory, formulated in greater detail, may be stated in the following terms, which I copy in all important respects from the memoir published by Rosenthal:—The tissues which compose the body of the animal, and which are themselves composed of carbon, hydrogen, oxygen and azote, possess the power of assimilating a further quantity of oxygen, a quantity somewhat greater than that which they already contain; and, by reason of this fact, they are able, as combustion advances, to accomplish two things—first, to combine with the surplus oxygen furnished by respiration; and, second, to form carbonic acid, water and certain azotic matters that are discharged from the body. It is this process of combustion which gives rise to heat in the animal’s body and in addition is associated with a certain loss in its weight. This loss, however, is limited, for the furnishing of new elements is going on simultaneously with the casting off of the old, thus restricting the loss of weight.

It is to Lavoisier that the imperishable honor belongs of formulating the chemical theory of respiration, and of thereby founding a new era in physiology—the modern era. (Claude Bernard.)

Too much stress cannot be laid upon the truth of this declaration made by Claude Bernard, the great modern authority in physiology, concerning this, the most important advance secured for the science of medicine during the eighteenth century. But alas! many years had to elapse before the physiologists of that period were able to appreciate the importance of Lavoisier’s discovery. Very soon after the announcement of this new theory the leading chemists of Europe returned almost as a single body to the old phlogiston doctrine.

Lavoisier’s portrait is shown in the frontispiece of the present volume.