HYPER TR OPHY 1 1 5 



far toward disproving the view that the power of regeneration has a 

 connection with the liability of a part to injury. 



HYPERTROPHY 



The hypertrophy, or unusual enlargement, of organs has long 

 attracted the attention of physiologists, and the extremely interesting 

 observations and experiments that have been made in this connection 

 have an important although an indirect bearing on the problem of 

 regeneration. Ribbert, as has been pointed out, holds that the 

 processes of hypertrophy and of regeneration stand in a sort of 

 inverse relation to each other, but it is doubtful, I think, if any such 

 general relation exists. Two kinds of hypertrophy are now generally 

 distinguished : functional hypertrophy, which takes place when a 

 part becomes enlarged through use ; and compensating hypertrophy, 

 which takes place when one organ being removed another enlarges. 

 The enlargement in the latter case may, of course, be brought about 

 by the increased use of the parts that enlarge, but as this is not 

 necessarily the case, the distinction between the two processes is a 

 useful one. The causes of compensating hypertrophy are by no 

 means simple, and several possibilities have been suggested to 

 account for the enlargement. The best ascertained facts in con- 

 nection with hypertrophy relate almost entirely to man and to a 

 few other mammals. 1 



By hypertrophy is meant an increase of the substance of which 

 an organ is composed. Swelling due to the imbibition of water or 

 of blood-serum is not, in a technical sense, a process of hypertrophy. 

 Virchow distinguishes two kinds of hypertrophy: (i) Hypertrophy 

 in a narrower sense in which the enlargement is due to an increase 

 in the size of the cells of which an organ is composed. This en- 

 largement of the individual cells leads of course to an increase in 

 the size of the whole organ. (2) Hyperplasy due to an increase 

 in the number of cells of which an organ is composed, which also 

 causes an enlargement of the whole organ if the cells retain the 

 normal size. The division into functional and compensating hyper- 

 trophy given above is a physiological distinction, and both of these 

 processes might occur in Virchow's subdivisions. 



Giants may be looked upon as hypertrophied individuals, since all 

 the organs of the body are larger than the normal. The enlargement 

 is, in this case, not due to external influences, but to some peculiarity 



1 The more generally accepted results are given in Virchow's Cellular Pathology and 

 in Ziegler's Pathological Anatomy. An excellent review of the subject down to 1895 

 is given in a summary by Ludwig Aschoff in the Ergebnisse d, allgetn. patholog. Morphol, 

 nnd Physiologic, 1895, "Regeneration und Hypertrophie," in which there are two hundred 

 and eighteen references to the literature. 



