THE WONDER OF LIFE 589 



are born old ; some telescope adolescence and others draw 

 it out for many years. It is plausible, and, as we say, 

 suggestive, to regard certain types as arrested juveniles 

 and others as precociously senile, just as we have plants 

 which remain as great buds and others which are all flower. 



The idea is the more valuable because we know of an 

 agency in higher animals by which the rate of development 

 of particular parts can be altered. It has been shown 

 that internal secretions have a regulating action on the 

 growth of parts of the body. Some act as accelerants, 

 others as inhibitors. It is said that ' infundibular extract 

 (from the pituitary body) has been employed with success 

 in recent years in order to add in a short time a few desirable 

 inches to a young man's height. So that it seems, after 

 all, as if one may, by taking sufficient thought, add a cubit 

 to one's stature. In other cases, it is the absence of a 

 specific secretion that causes some particular part to grow 

 abnormally large, as if some brake were removed. Prof. 

 Arthur Dendy has suggested that this internal regulation 

 of growth may account for cases where animals or parts 

 of animals seem to have acquired some sort of momentum, 

 growing far beyond the hmit of utihty. A disappearance 

 of certain glands, or some change in the secretion of certain 

 glands, may remove the normal brake, with the result 

 that a part which was wont to be controlled as to its 

 growth by a specific secretion or ' hormone ', may grow 

 far beyond its optimum, and may indeed become fatal to 

 its possessor. 



Another theory, deserving of more than brief illustration, 

 is suggested by Virchow's idea of an optimism of pathology. 

 Certain organic diseases are due to constitutional variations 

 which tend to the wrong side of viabihty, but those germi- 



