1 86 



VETERINARY PHYSIOLOGY 



reactions are brought about. With the cerebrum intact this 

 co-ordination is far more complete. 



The reactions are, in part at least, determined by 

 (1) The previous training and education of the brain. For, 

 just as in the spinal cord channels of action are formed, so in 

 the cerebrum, if a given reaction once follows a given stimulus, 

 it will tend to follow it again. (a) This training is in part 

 hereditary. Each individual of a race is born with well- 

 established lines of action in the process of development, and 

 throughout life these inherited channels play an important part 

 in determining the results of stimulation, (b) But it is also 



s~\ 



. - - - S OrVtUUs. 



-S-Coronalis 

 Homologu.e 

 of Rolando 



Rkinici, 



ECTOSYLVIAN. 

 TOSYLVIAN B... 



PARIETAL- - 



VISUAL 



S Uteralu. 



S Fctolateralis. 



Calcanne 



S PostliteraliJ. 



Poit-cilca.ri.rxe' 



OLFACTORY. A.. 



(T-EXTRA-RMINie. 



Fig. 97. Superior and inferior nspects of the brain of the dog to show the various 

 sulci and the distribution of the chief receiving and reacting mechanisms. 



largely acquired by the individual, since the reception of each 

 stimulus and the performance of a resulting action, however 

 this be determined, tends to lay down a path which will again 

 be followed. 



(2) Not only will the previous training of the brain thus act 

 as the directive force in the response to stimuli, but the 

 nutrition of the brain also plays an important part. The action 

 of a brain when well nourished and freely supplied with pure 

 blood is often very different to that of the same brain when 

 badly nourished or imperfectly supplied with healthy blood. 

 Since the education of the brain really consists in developing 

 proper responses to various stimuli, the importance of the brain 



