Disease and Its Causes by William Thomas Councilman (early reader books .TXT) 📕

which varies within slight limits, to the size of the body, a large individual having organs of corresponding size. Knowing that the capacity of growth is one of the inherent properties of living matter, it is much easier to understand the continuance of growth than its cessation. It is impossible to avoid the conclusion that there is some internal mechanism of the body which controls and regulates growth. In the first chapter reference was made to organs producing substances which pass directly into the circulation; these substances act by control of the activities of other parts, stimulating or depressing or altering their function. Two of these glands, the thymus, lying in front, where the neck joins the body and which attains its greatest size at puberty, and the pituitary body, placed beneath the brain but forming no part of it, have been shown by recent investigations to have a very definite relation to growth, especially the growth of the skeleton. The growth energy chiefly resides in the skeleton, and if the growing animal has a diet sufficient only to maintain the body weight, the skeleton will continue to grow at the expense of the other tissues, literally living upon the rest of the body. Disease of the glands mentioned leading to an increase or diminution or alteration of their function may not only inhibit or unduly increase the growth of the skeleton, but may also interfere with the sexual development which accompanies the skeleton growth.

The difficulties which arise in an endeavor to comprehend normal growth are greater when the growth of tumors is considered. A tumor is a mass of newly formed tissue which in structure, in growth, and the relations which it forms with adjoining tissues departs to a greater or less degree from the type of the tissue to which it is related in structure or from which it originates. It is an independent structure which, like a parasite, grows at the expense of the body, contributing nothing to it, and its capacity for growth is unlimited. A tumor cannot be considered as an organ, its activities not being coordinated with those of the body. A part of the body it certainly is, but in the household economy it is to be considered as a wild and lawless guest, not influenced by or conforming with the regulations of the household. The rapidity of growth varies; certain tumors for years increase but little in size, while others may be seen to increase from day to day. The growth is often intermittent, periods of great activity of growth alternating with periods of quiescence. The nutrition and growth of a tumor is only slightly influenced by the condition of nutrition of the bearer. Its cells have a greater avidity for food than have those of the body, and, like the growing bones of an insufficiently fed animal, growth in some cases seems to take place at the expense of the body, the normal cells not obtaining sufficient nutriment to repair their waste.

A tumor may be of any size: so small as to be invisible to the naked eye, or its weight may exceed that of the individual who bears it. The limitations to its growth are extrinsic and not intrinsic. There is no distinct color. Certain tumors have color which depends upon the presence of a dark brown or black pigment within the cells. Hæmorrhages within them are not infrequent, and they may be colored by the blood or by pigments formed from it. Usually they have a gray color modified by their varying vascularity, or the cut surface may be mottled due to areas of cell degeneration. The consistency varies; some tumors are so soft that they can be pressed through a sieve, others are of stony hardness. There is no distinct shape, this being influenced by the nature of the tumor, the manner of growth and situation. When the tumor grows on or near a surface, it may project from this and be attached by a narrow band only; in the interior of the body it may be irregular in outline, round or lobular, the shape being influenced by many factors. Tumors like the tissues of the normal body are nourished by the blood and contain blood vessels often in great numbers.

A tumor arises by the cells of a part of the body beginning to grow and taking on the characteristics of a tumor. Its growth is independent, the cells of the adjoining tissue taking no part in it. The tissue in the vicinity of the tumor is partly pushed aside by the mass, or the tumor grows into it and the tissue disappears as the tumor advances. The destruction of the surrounding tissue is brought about partly by the pressure which the tumor exerts, partly by the compression of the blood vessels or the blood supply of the organs is diverted to the tumor.

The characteristics of a tumor are due to the cells which it contains (Fig 14). These often become separated from the main mass and are carried by the blood into other parts of the body, where they grow and form tumors similar in character to the parent tumor. In the extraordinary capacity for growth possessed by tumor cells, they resemble vegetable rather than animal cells. There is no limit to the growth of a tumor save by the death of the individual who bears it, thus cutting off the supply of nutrition. The cells of tumors peculiar to man show a narrow range of adaptation. They will grow only in the body of the individual to whom the tumor belongs, and die when grafted on another individual. In the case of tumors which arise in animals, pieces of the tumor when grafted on another animal of the same species will grow, and in this way the growth capacity of the tumor cells has been estimated. Thus, by transplanting a small section of a mouse tumor into other mice, the small transplanted fragments will in two weeks grow to the size of filberts, and each of these will furnish material to engraft upon ten mice. These new tumors are similar in character to the original tumor, and really represent parts of it in the same way that all the Baldwin apples in the world are parts of the original tree which was found in Baldwinville many years ago, and as all the Concord grape vines are really parts of the original vine. It has been estimated that if all the growth capacity of this mouse tumor were availed of by the successive inoculation of other mice, a mass of tumor several times the diameter of the sun would grow in two years. The condition of the individual seems to exert no influence upon the growth of the tumor. Growth may be as rapid when the bearer is in a condition of extreme emaciation as it is when the bearer is well nourished and robust.

Fig. 14—Photograph Of A Microscopic Preparation From A Cancer Of The Uterus. A large mass of cells is extending into the tissue of the uterus which is shown as the fibrous structure. Such a cell mass penetrating into the tissue represents the real cancer, the tissue about the cell masses bear the blood vessels which nourish the tumor cells.

Fig. 14—Photograph Of A Microscopic Preparation From A Cancer Of The Uterus. A large mass of cells is extending into the tissue of the uterus which is shown as the fibrous structure. Such a cell mass penetrating into the tissue represents the real cancer, the tissue about the cell masses bear the blood vessels which nourish the tumor cells.

Those tumors which grow rapidly and invade and destroy the surrounding tissue are called malignant tumors or cancers, but in a strict sense no tumor can be regarded as benign, for none can serve a useful purpose. A tumor after a period of slow growth can begin to grow rapidly. Tumors may arise in any part of the body, but there are certain places of preference particularly for the more malignant tumors. These are places where the cells naturally have a marked power of growth, and especially where growth is intermittent as in the uterus and mammary gland.

Little is known in regard to the influence of inheritance on the formation of tumors. Study of the tumors of mice show a slightly greater susceptibility to tumor formation in the progeny of mice who have developed tumors. Studies of human families seem to show that heredity has a slight influence, but in the frequency of tumors such statistical evidence is of little value. The question of inheritance has much bearing on the origin of tumors. If the tumor is accidental and due entirely to extraneous causes, inheritance is not probable; but if there is some predisposition to tumor formation in certain individuals due to some peculiarity, then inheritance may exert an influence.

The question as to whether tumors are an increasing cause of disease is equally difficult of solution. The mortality statistics, if taken at their face value, show an enormous increase in frequency; but there are many factors which must be considered and which render the decision difficult and doubtful. Tumors are largely a prerogative of age, and the increased duration of life which preventive medicine has brought about brings more people into the age when tumors are more common. Owing to the greater skill in the diagnosis of tumors, especially those of the internal organs, they are now recognized more frequently and more deaths are correctly ascribed to them. Deaths from tumors were formerly often purposely concealed and attributed to some other cause.

No age is immune to tumors. They may be present at birth or develop shortly afterwards. The age from five to twenty years is the most free from them, that from forty-five to sixty-five the most susceptible, particularly to the more malignant forms.

A tumor is a local disease. The growing tissue of the tumor is the disease, and it is evident that if the entire tumor were removed the disease would be cured. This is the end sought by surgical interference, but notwithstanding seemingly thorough removal, the tumor often reappears after an interval of months or years. There are many conditions which may render the complete removal of a tumor difficult or impossible. It is often impossible to ascertain just how far the tumor cells have invaded the neighboring structures; the situation of the tumor may be such that an extended removal would injure organs which are essential for life, or at the time of removal the tumor cells may have been conveyed elsewhere by the blood or lymphatic vessels.

Successful removal depends mainly upon the length of time the tumor has been growing. At an early stage even the most malignant tumor may be successfully removed. It is evident from this how disastrous may be the neglect of proper surgical treatment of a tumor. The time may be very short between the first evidence of the presence of a tumor and the development of a condition which would render complete removal impossible.

The effect of a tumor upon its bearer depends upon its character and situation. Pain is very commonly present, and is due to the pressure which the growing tumor exerts upon the sensory nerves. Pain may, however, not be present or appear only at the last. A condition of malnutrition and emaciation often results due to the passage into the blood of injurious substances formed in the tumor, or to the destruction of important organs by the growing tumor. The growth of a tumor in the intestine may obstruct or close the canal and thus interfere with nutrition.

The cause or causes of tumors are unknown. We know that the tumor represents essentially an abnormal growth, and that this growth is due to new formation of cells. In certain cases the tumor repeats the structure of the organ or tissue in which it originates, in others it departs widely from this; always, however, its