DILATATION AND CONTRACTION.
When different organs or parts of the body are subjected to strain or to irregular work they change in their dimensions, and to these changes different terms are applied. When a hollow structure, such as the heart, or an artery, or a vein, is dis tended without being enlarged in its own structure, it is said to be suffering from dilatation. When, on the other hand, it is re duced in calibre, it is said to be suffering from contraction.
Hypertophy or enlargement.
Sometimes it happens that an organ or part is increased in size, throughout its entire substance, beyond what is natural. A common illustration of this state is shown in the muscles of the working, or hammer-arm of the blacksmith. To this condition of enlargement the term hypertrophy is applied.
Atrophy or wasting.
An organ or part of the body may undergo just the opposite change from that described under the head hypertrophy. It may become smaller, from having wasted, under which circumstances the word atrophy is used to express the change that has been produced.
The words, dilatation, contraction, hypertrophy, atrophy, are of common use in the literature of disease, and their general meaning should be carefully remembered. The terms may be applied to any organ. Thus in diseased conditions of the heart, to cite a common example, the heart may be dilated, contracted, hypertrophied, or atrophied.