BIOLOGY IN ITS WIDER ASPECTS 1223 



how the wind has been blowing. The medical importance of the 

 study of "nurture" — alimentary, functional, and environmental — is 

 obvious. 



Hints from Zoology. — We have seen that zoology has made 

 stable contributions without which medical science would not stand 

 as it does to-day. But there are scores of investigations which do not 

 at present offer more than hints. Thus, to begin at the beginning 

 of life, it seems unlikely that there is not some medical application 

 for the facts of artificial parthenogenesis or aspermic development. 

 The researches of Delage, Loeb, Bataillon, and others, have shown 

 that it is possible in a variety of ways to set an egg-cell developing 

 without its being fertilised ; and that if this artificial start is speedily 

 steadied by replacement in normal conditions, a quite normal 

 development may result. This has been effected in many cases, in 

 sea-urchin, in sea-worm, in mollusc, and as high up as frog. The 

 sea-urchin ovum may be activated by dilute butyric acid or by a 

 mixture of tannin and ammonia; the frog ovum may be activated 

 by pricking with a needle, and a subsequent douche of blood. Now, 

 suppose we could correlate this artificial stimulation of ovum 

 development with the strange growth of galls which follows physio- 

 logical stimulus from the salivary secretion of the larval gall insect, 

 and with the stimulus that induces the regeneration of a lost part — 

 a starfish's arm, a lizard's tail — ^we might perhaps get some indirect 

 light on an obscure problem like that of certain abnormal (terato- 

 matous) growths in Man. 



Or to go to the other end of life, a great deal of zoological work 

 has been done on the normal ageing or senescence of animals. Every- 

 thing points to the conclusion that what really ages is the fine 

 colloidal framework of the cells; not the living matter so much as 

 the furnishings of the cellular laboratory. In simple animals, up to 

 planarian worms, the length of life's tether seems indefinitely long, 

 for processes of rejuvenescence are continually counteracting those 

 of senescence. Should there not be more serious and ambitious 

 study of man's possibilities in the way of rejuvenescence? 



The busy bee was one of the exemplars of our childhood. It 

 certainly improves each shining hour, but with an excess of zeal 

 which seemed to us very fatuous, and we were right ; for the shining 

 hour does not improve the busy bee. It grows old rapidly, and has 

 a very short life. Its brain-cells go quickly out of gear; their micro- 

 scopical examination shows the effects of nerve tiredness at the end 

 of a busy day, and the effects of nerve fatigue at the end of a mid- 

 summer month. As Professor Hodge says: "The nerve-cells, in the 

 course of the bee's daily work, gradually cease to be functional, 

 and die off until no more are left than are sufficient for the neces- 

 sary vital functions." Hodge's work on the bee suggests that there 

 are three grades of nervous "wear and tear": (i) There is normal 



