ATEOPHY AND DEGENEKATIONS OF TISSUE. 69 



organs. Infiltration occurs in both the young and old, and is 

 associated with a general obese condition of the whole system. 



NUTRITIOiSr INCREASED. 



Opposed to the conditions of atrophy and the degenerations, is 

 that of increased nutritive activity, or hy2)ertrophy. In hyper- 

 trophy there is an absolute increase of the normal tissues of a 

 part, resulting from an increase in its functional activity. 



Hypertrophy, although sometimes depending on disease, is of 

 itself a compensating process, whereby injury from damage to an 

 important organ may be avoided ; as, for example, in the thick- 

 ened condition of the heart in disease of the valves, and in the 

 same condition of that organ when not associated with any disease, 

 but arising from the animal being repeatedly forced to severe 

 trials of strength and endurance, in racing, hunting, &c. In 

 the first instance the hypertrophy of the cardiac walls arises from 

 the necessity of a more powerful contraction for the purpose 

 of overcoming valvular obstruction, and sending a due supply 

 of blood to the various organs of the body, and in the other 

 case of contracting powerfully to attain the same end, during 

 repeated and severe exercise. 



As a physiological process, hypertrophy of muscular tissue is 

 produced by the process of training, where the muscles of the 

 whole body are enlarged, strengthened, and made capable of per- 

 forming extraordinar;^ feats of strength and endurance. "Who 

 can fail to see in a well-trained racehorse the muscles standing, 

 as it were, prominently one from another about the quarters and 

 thighs, " hard as iron " to the touch, and giving the animal an 

 appearance of being thin and poor. The appearance of thinness 

 is the result of the great prommence of each individual muscle, 

 of increase in their volume and weight, and an extraordinary 

 healthy tonicity. 



"The cause of real hypertrophy seems to be always the 

 increased exertion of the organ ; more than usual effort is de- 

 manded of it, and according to the law of the cu'culation, which 

 we have noticed, more blood flows to the part than usual. This, 

 if the organ be in a healthy state, not only supplies its waste, but 

 furnishes material for increase and development. The heart in 

 various diseased states of its valves, the urinary bladder in stric- 



