OTHER PHYSIOLOGISTS. 595 



way of explanation, he says again, "If you ask 

 me for the cause of the first life, I answer your 

 question by another : What is the cause of gra- 

 vitation, chemical affinity, &c. but the Causa 

 Causarum? the Deity himself?" (Life, Health, 

 and Disease, pp. 6672.) 



But why should I quote further examples of a 

 doctrine which is taught by nearly all modern 

 physiologists, and by some of them carried even 

 further than was ever contemplated by Cullen ? 

 Having already shown that nervous influence is 

 not the cause, but a secondary effect of vital 

 energy, it may be right to show, by a brief re- 

 ference to comparative physiology, that the mus- 

 cular strength and locomotive power of animals 

 are not in any proportion to the developement of 

 the nervous system. As a striking example of 

 this, the brain of man is perhaps fifty times larger 

 than that of the ostrich, which is no less remark- 

 able for stupidity, than for its prodigious mus- 

 cular power ; for if we are to credit the accounts 

 of travellers in Africa, it has been known to sur- 

 pass the fleetest race-horse, with a full-grown 

 negro on its back. She does not, however, seem 

 to be ignorant of the fact, that her eggs may be 

 hatched by the agency of solar heat, independent 

 of nervous influence, when buried in the hot sands 

 of Senegal, where she sits on them only at night. 



The brain of the greyhound, like that of the 

 fox, hare, rabbit, goat, deer, and many other 



