838 



Comparative Animal Physiology 



which have been studied is there certain representation of the hind hmbs 

 and tail.^- - Removal of the excitable area from the opossum causes tempor- 

 ary weakness of the fore feet, and stimulation of the striatum then elicits 

 movement of contralateral legs.-^"^ Removal of cortex plus striatum causes 

 partial contralateral paralysis, and failure to climb or maintain balance. How- 

 ever, the animals can eat if food touches the mouth. The face is well repre- 



Focial 



Fore limb 



A 



Fore limb 



B 



Focial ond 

 masticatory 

 (including facial 

 vibrissae movements) 



CAT 



Hind limb Sulcus centroles Rolandi 



J°''--Oi!«S*''----^ Trunk 

 Fore limb - 



MACAQUE 



Fig. 311. Diagrams showing distribution of excitable cortex. A, in the laboratory rat. 

 B, In the cat. C, In the macaque monkey (Pitneciis). From Huber."" 



sented in the motor cortex. In the hedgehog Erinaceus the neocortex is rela- 

 tively small, and electrical responses to chemical stimulation of the olfactory 

 organ** are observed in both the pyriform area and the olfactory bulb. The 

 motor cortex is less active and less defined than in more specialized mam- 

 mals;^^ the cortex of the sheep is not much better. 



In rodents there are widely dispersed excitable areas, electrical stimula- 

 tion of which elicits discrete movements of groups of muscles (Fig. 311, A). 

 Decorticate rabbits survive well; they appear blind at first, but later can dis- 

 tinguish light and darkness.^"-* In dogs, when all of the cortex is removed. 

 the deficiencies are more severe. The animals are blind, although the pupils 

 constrict to bright light, and thev are nearly deaf; they lose all those re- 

 sponses which depend on past training, but are able to stand and to make 

 many postural responses. 



Localization in the cortex of primates, which is distinctly superior to that 

 in any other mammal, has been extensively studied;^^"* only a few aspects of 

 it can be mentioned here. There is a striking series from lemurs through the 

 anthropoids to man. One viewpoint is that specific functions are precisely 

 localized; another opinion is that the cortex functions as a whole, or at least 

 by areas in which finer localization is not rigidly fixed. In a general way the 



