158 Journal of Comparative Neurology. 



be desired. No opportunity was offered to obtain the medulla 

 spinalis of the whale, the largest of the living mammals, and 

 likewise all efforts have so far failed to obtain a specimen of the 

 small shrews (Soricidae) some of which {Sorcx pcrsonatus, per- 

 haps) are among the smallest of North American mammals, 

 with the probable exception of the much more rare Pcrotnysciis 

 taylon of southwestern Texas. Failing to get a specimen of 

 Sorex personatus, the small brownish gray bat, Atalapha cinerea, 

 had to be used instead. Therefore, the series begins with the 

 elephant and ends with the bat, and the intermediate members 

 were chosen with as much regard to a gradual variation in body 

 weight as convenience in obtaining them would allow. Only 

 adult animals were used. The position of an animal in the 

 series was determined by an estimation of the normal adult 

 body weight of the species. In the case of the dog, where 

 the numerous varieties afford a wide range in the adult body 

 weight, the specimen chosen was a hound both because of the 

 medium size of this variety and because its body weight would fall 

 in the series about mid-way between that of the monkey, where 

 there was no choice at the time, and that of the hog employed. 

 A hound was thought to be the best of several varieties of similar 

 size, because in such, the proportion between body weight and 

 nervous system is perhaps more nearly normal for the species, 

 Canis familiatis, than in other varieties and especially better 

 than in either a very small or very large variety of dog. It is 

 well known that in the small varieties, obtained by cultivation 

 and artificial selection, the central nervous system is exception- 

 ally large in proportion to the size of the body, while, on the 

 other hand, the size of the large varieties consists more in an 

 over-development of the muscular and osseous systems than in 

 an attendant increase in the volume of the central nervous 

 system. 



Since it was impossible to get the intact weight of certain 

 members of the series, none of the others were individually 

 weighed. In fact their individual weight was not considered 

 of so much importance. The position of each in the series was 

 rather determined by an estimation of the average weight of its 



