TJie Relative Size of Red- Blood Corpuscle and Braui. 3 i 



power of flight) is absent. We cannot claim for it the greatest ac- 

 tivity or rapidity of motion ; it has the largest red corpuscle (-g| ^), 

 and a brain of inverse ratio to the body ; its temperature is less than 

 that of the smaller and more active members of its class, as the 

 Wren and Humming Bird, the latter being the smallest and most 

 active of them all. The respiration of the ostrich is 24 per minute, 

 this being slower than that of any other bird ; in the humming bird 

 the respiration is 60 per minute, this together with a temperature 

 of 4° Y. higher than that of any other bird, it being 112" F. im- 

 plies a greater rate of molecular change, and a greater rate of 

 molecular change enables a smaller nervous system to generate an 

 amount of motion which would require a larger nervous system if 

 the rate of molecular change were less. The brain in this bird 

 (Humming) is much greater in proportion to the size of the body, 

 it being i : 11 ; it has the smallest known corpuscle among birds, 

 measuring t"2"6 66 of an inch in diameter, it is proverbial for activ- 

 ity, having been known to visit one hundred flowers in one minute. 



The nerve tube or fibre of birds varies is from , o'o ••O i o'bo '•^'^ 

 an inch in diameter. 



We now come to the fourth subdivision, that of mammals, 

 and the last to be considered. 



In mammals we find the most intelligence, physical and men- 

 tal endurance, the largest and most complex nervous and mus- 

 cular system; they constitute all living vertebrates that suckle their 

 young, including a few aquatics, such as the whale, walrus, seal, 

 sea-lion, and manatee. 



The ratio of die brain to the body in mammals in general is 

 I : 186, while the temperature ranges from 37'' F. to 98.7° F.; rel- 

 atively they have the greatest number of red blood corpuscles, the 

 size ot which varies from 2T4T ^o , oJoo o^ ^^^ mc\\ in diameter ; the 

 most active animals are those having the highest degree of temper- 

 ature, the smallest red corpuscle, and the largest cerebellum in pro- 

 portion to the weight of the body ; the brain of mammals differs fro n 

 all other vertebrates, in that the commissures of the hemispheres 

 and cerebellum, pass acros? the medulla, thus forming the corpus 

 collosum and pons' varolii ; those of the cerebrum are more exten- 

 sive in depth, and number than in either the bird, reptile or fish. 



The ratio of the size of the brain to the weight of the body 

 is not so great in passing from the larger to the smaller of this class 

 as is that of birds, this same law governs the size of their red co; - 

 pucle. 



