As a consequence of increase of nutrition we have a condition known commonly as _hypertrophy_, more accurately as _hyperplasia_. Hypertrophy literally means overgrowth, whereas hyperplasia more accurately describes that which constitutes hypertrophy--namely, numerical increase of constituent cells. Common usage has made the more inaccurate name “hypertrophy” cover nearly all these conditions. _Hypertrophy_, or hyperplasia, _means enlargement of a part or of an organ beyond its usual limits_, and as the result of increased function or increased nutrition. It is to be distinguished from _gigantism_, which means inordinate enlargement as the result of a congenital tendency or condition. Hypertrophy is-- A. _Physiological_ {1. Compensatory; {2. From deficient use. {3. Local; B. _Pathological_ {4. General; {5. Senile; {6. Congenital. [Illustration: FIG. 1 Congenital hypertrophy: gigantism of both lower extremities. (Case of Dr. Graefe [Sandusky].)] A. =Physiological Hypertrophy.=--1. This includes many of the compensatory enlargements of an organ or a part when extra work is put upon it, owing to deficiency of some other organ or part. This is spoken of as _compensatory_ enlargement. Illustrative examples may be seen in the heart, which becomes larger and stronger when the bloodvessel walls are diseased and their lumen narrowed, or when other obstructions to circulation are brought about; again, in enlargement of one kidney after extirpation of the other, or of the wall of the stomach when the pylorus is constricted or obstructed; again, of the fibula after weakening or more or less destruction of the tibia, or of the shaft of any bone when it has been weakened at some point by not too acute disease; or, again, of the walls of bursæ after constant friction. 2. The best examples of physiological hypertrophy owing to deficient use are perhaps seen in some of the lower animals; as, for instance, in the teeth of such rodents as beavers when kept in captivity and prevented from natural use.