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Page 16
CHAPTER III
THE GROWTH OF THE BODY.--GROWTH MORE RAPID IN EMBRYONIC PERIOD.--THE
CO�RDINATION AND REGULATION OF GROWTH.--TUMORS.--THE GROWTH OF TUMORS
COMPARED WITH NORMAL GROWTH.--SIZE, SHAPE AND STRUCTURE OF TUMORS.--
THE GROWTH CAPACITY OF TUMORS AS SHOWN BY THE INOCULATION OF TUMORS OF
MICE.--BENIGN AND MALIGNANT TUMORS.--EFFECT OF INHERITANCE.--ARE
TUMORS BECOMING MORE FREQUENT?--THE EFFECT PRODUCED BY A TUMOR ON THE
INDIVIDUAL WHO BEARS IT.--RELATION OF TUMORS TO AGE AND SEX.--THEORIES
AS TO THE CAUSE OF TUMORS.--THE PARASITIC THEORY.--THE TRAUMATIC
THEORY.--THE EMBRYONIC THEORY.--THE IMPORTANCE OF THE EARLY
RECOGNITION AND REMOVAL OF TUMORS.
The power of growth is possessed by every living thing, but growth is
not limited to the living. Crystals also will grow, and the rapidity
and character of growth and the maximum size of the crystal depends
upon the character of the substance which forms the crystal. From the
single cell or ovum formed by the union of the male and female sexual
cells, growth is continuous until a size corresponding to the type of
the species is attained. From this time onward growth is limited to
the degree necessary to supply the constant loss of material which the
body undergoes. The rapidity of the growth of the body and of its
component parts differs at different ages, and becomes progressively
less active from its beginning in the ovum until the adult type of the
species is attained. As determined by the volume, the embryo increases
more than ten thousand times in size during the first month of
intra-uterine life. At birth the average weight is six and a half
pounds; at the end of the first year eighteen and a half pounds, a
gain of twelve pounds; at the end of the second year twenty-three
pounds, a gain of four and a half pounds. The growth is co�rdinated,
the size of the single organs bearing a definite ratio, 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.
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