28 Cincinnati Society of Natural History, 



ion ; but one of the greatest difficulties to overcome is the want of 

 a more extended investigation. 



The first class to be considered is the lowest of Vertebrates, 

 viz : cold-blooded animals, commonly known as fish. Their tem- 

 perature averages 1.70° C. (35.06° F.), while the ratio of the 

 weightofthe brain to the body isone to five thousand six hundred and 

 sixty eight, (i ; 5668). We find in the shark a smaller brain compared 

 to the size of the body, than in any other fish ; while in the carp 

 we find the largest brain, in proportion to the size of the body, the 

 proportion being 1 : 560, and the corpuscle measure aV*^ inches 

 in diameter, the shark having a brain that weighs n^^-^ of weight 

 of body, and a corpuscle that measures ^^40 inch in diameter. 



As you see there is a marked difference in the degree of ac- 

 tivity and the power of generating force in these two fish. 



The primitive nerve tube or fibre in its natural state is perfectly 

 cylindrical, measuring in the eel ,^'^3 of an inch in diameter ; this 

 being the largest found among fish. 



The following measurements, although rather limited in number, 

 will show the inverse ratio of the size of the brain to the body, and 

 of the size of the red blood corpuscle to the brain, the measure- 

 ments being taken in the fractions of an English inch. 



Size of brain to body 



Shark 1 : 5668 



Pike 1:1 305 



Carp I : 560 



Size of corpuscle. 



Shark 1:1142 



Ed 1:1745 



Sturgeon i : 1 900 



Perch I : 2090 



Carp I : 2142 



In passing from the lower to the higher Vertebrates, we have 

 next to consider the class of reptiles. 

 They are of three divisions, viz : 



Chelonians, (Tortoise). 



Saurians, (Lizards). 



Ophedians, (Serpents), 

 In embryology they are closely allied to birds ; their tempera- 

 ture is but a little higher than that of fish, it being 4.5° C. (40. i" F). 

 The pulmonary circulation of this class is very incomplete, a 



