HYPERTROPHY. 397 



providing more than the previous power to meet a par- 

 ticular emergency ; the other may be the result of a deposit 

 of morbid material within the natural structure of the part 

 diminishing, instead of augmenting, its fitness for its office. 

 Such a healthy process of growth in a part, attended with 

 increased power and activity of its functions, may, however, 

 occur as the consequence of disease in some other part ; in 

 which case it is commonly called Hypertrophy, i.e., excess 

 of nutrition. The most familiar examples of this are in 

 the increased thickness and robustness of the muscular 

 walls of the cavities of the heart in cases of continued 

 obstruction to the circulation ; and in the increased 

 development of the muscular coat of the urinary bladder 

 when, from any cause, the free discharge of urine from it 

 is interfered with. In both these cases, though the origin 

 of the growth is the consequence of disease, yet the growth 

 itself is natural, and its end is the benefit of the economy ; 

 it is only common growth renewed or exercised in a part 

 which had attained its size in due proportion to the rest of 

 the body. 



It may be further mentioned, in relation to the phy- 

 siology of this subject, that when the increase of function, 

 which is requisite in the cases from which hypertrophy 

 results, cannot be efficiently discharged by mere increase 

 of the ordinary tissue of the part, the development of a 

 new and higher kind of tissue is frequently combined with 

 this growth. An example of this is furnished by the 

 uterus, in the walls of which, when it becomes enlarged 

 by pregnancy, or by the growth of fibrous tumours, organic 

 muscular fibres, found in a very ill-developed condition in 

 its quiescent state, are then enormously developed, and 

 provide for the expulsion of the foetus or the foreign body. 

 Other examples of the same kind are furnished by cases in 

 which, from obstruction to the discharge of their contents 

 and a consequently increased necessity for propulsive 

 power, the coats of reservoirs and of ducts become the seat 



