Surgery, in contradistinction to medicine, as a separate branch of the healing art, includes all manual procedures and is not limited to cutting operations exclusively. It is that branch which deals with the treatment of morbid conditions by means of manual or instrumental agencies.

Morbid conditions include three distinct classes: those due to

Injuries. To this class belong all the processes due to physical agencies and it includes besides traumatism, the effects of heat and cold, of chemicals, of light and of electricity.

Infections. These may be either local or general. The reaction might occur at the point of entrance of the bacteria, or constitutional symptoms may evidence their invasion into the blood, or the absorption of their toxic products.

Many conditions in this class are linked closely with those in the following class:

Diseases. Here are classified (a) new growths, both benign and malignant; (b) changes due to age and environment, and (c) diseases not belonging in either of the above classes. These latter are generally known as idiopathic or spontaneous in their etiology. These terms, however, often indicate only a limit of knowledge as to their true etiology.

The Tissues. The tissues of the body, though apparently so different and varying so decidedly in their functions, are in many respects similar.

Every tissue is composed of two parts: the cellular elements and the intercellular substance. These are called cells and stroma. Upon the first of these depends the vitality and function of the part, while its density, shape and general physical properties are determined by the second. Likewise along the same lines of reason, all of our organs have two separate areas of tissue: the parenchymatous and the interstitial. The first contains the functioning and the second the supporting elements.

The physical conditions of the interstitial tissue or the intercellular substance vary greatly in density. Blood is a tissue, the intercellular constituent of which is fluid, and as we consider more dense tissues, we encounter all degrees of density of the framework or intercellular substance, until with the additional presence of calcareous elements, we conceive the hardness of bone and dentine. Tissues as a whole, however, are not solid; there are spaces in the supporting structure to admit of the passage of arteries, veins, nerves, and lymphatics.

Abnormal conditions arise in the various parts of the tissues. Certain diseases affect the parenchymatous tissue in an organ more than the interstitial tissue and again others affect the blood vessels particularly.

There may be hypertrophy, in which the entire organ or part becomes larger as a whole, the active cells and stroma sharing alike in the process, or there may be an hyperplasia, in which the active cells of the part proliferate abnormally. When the interstitial tissue alone develops excessively it is known as an infiltration. Under such circumstances the parenchymatous cells often undergo what is termed pressure atrophy; they are diminished by squeezing.

Atrophy of the part or organ, from whatever source, signifies its diminution in size; its function is, of course, either impaired or suspended as the process goes on.

The efforts on the part of the organism as a whole to combat or repair injury, bacterial invasion and disease are directed along definite lines. The study of these functions does not rightly come within the scope of these pages, belonging to physiology, but must be considered here, if only in brief for the purpose of a good understanding of the processes at work in surgical conditions.

As surgeons, the functions which concern us most are the

THE NERVOUS SYSTEM

The nerves operate in harmony with each other and with the organs to maintain health. The nervous system comprises the brain, the spinal cord, the nerves, and the ganglia. Aside from presiding over the special senses, this system controls and directs the processes of defense and repair. In doing so, the force and frequency of the heart beat, the calibre of the vessels and the chemistry and composition of the blood are all altered.

These phenomena are the ones which concern us in our present subject, acting as they do upon the blood and the organs which contain it. They will be considered more fully in the following:

THE CIRCULATORY SYSTEM

In health and disease the force and frequency of the heart beat and the calibre of the arteries undergo momentary alterations to meet changes surrounding us.

Dilatation and constriction of the arteries, and arterioles through the activity of the vasomotor nerves, permit of increasing and diminishing amounts of blood reaching the various organs and regions of the body. In this way the peripheral circulation, through the activity of the heat centre in the brain, acting upon the superficial capillaries, maintains the normal temperature of the body during the changes of season. In winter, heat conservation is effected by vaso-constriction of the superficial capillaries, while in summer, heat radiation is accomplished by vaso-dilatation together with the evaporation of moisture so abundantly supplied by the active sweat glands. Other phenomena demonstrating the vasomotor function are blushing, going pale, and the redness and swelling following injury or infection. Of the latter we will treat under the heading “Inflammation.”

Certain changes also occur in the blood in order that it may perform its functions. These changes are found both in the chemistry of its fluid content and in the number and kind of its solid elements: the corpuscles. The blood is a tissue; its corpuscles are the functioning cells and its fluid content the basement substance.

In the fluid content of the blood or plasma, as it is called, certain chemical changes occur in its fibrin-forming capacity. Clot formation, an effort on the part of the economy to arrest hemorrhage, is thus facilitated when there is active bleeding, also during labor and certain diseases.

The number and kind of white blood cells also undergo changes, as we shall see, under circumstances in which the defences of the organism are called into operation, for it is the function of the white blood corpuscles to combat bacterial invasion.

It is the preponderance of these white cells which imparts the peculiar milky color to pus.

Nourishment and oxygen are carried to the tissues by the red blood corpuscles. Under circumstances which we shall see later, these are also altered both in number and in size, and also in their arrangement in the vessels. (See Chapter IV, “Inflammation.”)

THE LYMPHATIC SYSTEM

Waste material in the tissues is carried off by the return blood in the veins and also by the lymphatics. These are in reality the scavengers of the body, both the lymphatic vessels and glands, performing important functions for the good of the economy. They are found beneath the skin and in the subcutaneous tissue, also along the course of the great veins.

The lymphatics far exceed the veins in number and perform a function similar to the veins, gathering waste material from the tissues, also the digested food called chyle, from the stomach and intestines. The lymphatic vessels, also the lacteals which absorb the chyle, all pass through glands, which are extremely numerous, where certain deleterious substances are extracted from the lymph before it is emptied into the blood stream.

The lymphatic glands in performing their function as filters often become inflamed and when large numbers of pathogenic bacteria, or very virulent ones are contained in a gland, abscess formation results just as it would in any tissue so invaded.