180 



VETERINARY PHYSIOLOGY 



cutaneous sensations are evoked and our muscle-joint sense 

 is aroused. 



But, unless these sensations are brought together and 

 integrated, we can have no recognition that some one object, 

 a pine tree, is calling them forth. It is only by an 

 association of the sensations that wo gain the knowledge that 

 all are due to the object which we agree to call a pine tree. 



If, at a later date, some of these different sensations 

 called forth by this tree are again elicited, they are associated 



HolecuUr 



Co»nbin«d 



5uprA h 



Infra- 



Cranul&r 



■«54 



>-67« 



MoleculA/ I 





iGranuUrlB 



IflfrA I 



216 



S75: 





r- 



176; 



753 



•a»; 



i_ 



^V]leculArI 



Cra/Ktar ja 



l>tf.m ! 



^4a4iCnuHiJ»»'; 



»77 



■«3& 



>K>r7 



14" 



2J6 



>ii» 





MM 



>»' 



dtpth -032 mm 



Total 

 depth 



I J95mjn. 



depU. 



I 89i 



Total .^ 

 depth *» 



4MontKa FcEtus 



New bom Child 



Normal Hu/rvan Adult 



The Mole. 



Fig. 90. — To show the development of the diflferent layers of the cortex in 

 man, and their condition in one of the lower mammals — the mole. The 

 first column shows the two layers, from the lower of which the infra- 

 granular, granular, and supra-granular layers of the adult cortex are 

 formed. The second column shows the cortex at the time of birth. 

 The third column shows the growth of the supra-granular layers as 

 adult life is reached. In the fourth column the cortex of the adult 

 mole is shown for comparison. (After Bolton.) 



with the past impressions and again call forth the idea of 

 the pine tree and may lead us to conclude that we are 

 near one. 



This means that each sensation and each combination of 

 sensations or perceptions of the object producing them must 

 leave an impress on the brain which is the physical basis of 

 ^memory, and that the repetition of some of them, by 



