HYPERTROPHY. 285 



also atrophies from disease, as, for example, the gut below a 

 lumbar colotomy, which becomes the size of one's little finger. 

 There are many instances of atrophy due to disturbances of 

 normal nerve-influences, as that resulting in the salivary gland 

 after cutting off its nerve-supply. 



Atrophy is usually associated with other degenerative 

 changes, especially fatty degeneration and calcification. Ac- 

 companying the atrophy of the cells proper of a tissue there 

 is often an increase in its connective tissue, as, for instance, in 

 pseudohypertrophic paralysis. In the liver and kidney this 

 increase in connective tissue cirrhosis is often looked upon 

 as an evidence of chronic interstitial inflammation in contra- 

 distinction to parenchymatous inflammation. 



Hypertrophy. 



The term hypertrophy, which properly means over-feeding 

 or over-nourishment, is applied to an overgrowth of an organ, 

 without marked alteration from the normal structure. It 

 implies more than mere enlargement. A carcinomatous liver 

 is enlarged, but not hypertrophied. 



In true hypertrophy there is an increase only in the size of 

 the cells. Hyper 'plasia, or numerical hypertrophy, is an in- 

 crease in their number, their size not being increased but 

 even diminished. Physiologically this condition is seen in the 

 enlargement of the uterus following impregnation, and gigan- 

 tism is a remarkable example of general hypertrophy. Patho- 

 logically, in leukaemia, the spleen is found hypertrophied to 

 several times its normal size and weight. 



Causes : Increased functional activity, which means also in- 

 creased nourishment, is a most important factor in the pro- 

 duction of many hypertrophies. When increased work is 

 thrown upon the heart, for example as the result of valvular 

 disease, it becomes hypertrophied. Stricture of the urethra 

 causes hypertrophy of the walls of the bladder. When one 

 kidney is removed there is a compensatory hypertrophy of its 

 fellow. So also when part of a secreting gland, like the liver 

 or pancreas, is removed there is often a hypertrophy of the 

 remaining portion. 



