854 



COMPARATIVE ANATOMY 



The nose connects with the olfactory bulb and hemisphere. (Some 

 writers have considered the olfactory hemisphere an actual portion of the 

 brain equivalent to the cerebral hemisphere in man. These olfactory 

 hemispheres are, however, only portions of the olfactory apparatus.) 



The important point is to note that definite brain regions are set 

 aside for sensory impressions, and to notice that they are all on the dor- 

 sal surface (except a part of the olfactory centers). 



These regions which Professor Herrick understandably calls "nose 

 brains," "eye brains," "ear brains," "visceral brains," "skin brains," etc., 

 show the simplest type of the pattern of functional localization of pri- 

 mary reflex centers. That is, all these special "brains" or centers show 

 that practically all of the parts of the brain (except the cerebellum) have 

 a very definite connection with some particular peripheral organs. 



This means that this type of simple brain is concerned, in so far as 

 we can tell (with the exception of the cerebellum), only with simple 

 reflex action, there being no larg^e centers for the higher type of adjust- 

 ment found in the higher vertebrate brains. However, in the higher 

 vertebrates, even including man, there is this same type of simple con- 



A. B. 



Fig. 478. 



A, The brain of the dogfish, seen from above, cb., cerebellum; cer., cerebrum; 

 m.o., medulla oblongata ; olf.l., olfactory lobe ; olf.o., olfactory organ ; op.. 

 ophthalmic branches of fifth and seventh nervas ; op.l., optic lobes ; p.st., pineal 

 stalk ; r.b., restiform body ; sp.c., spinal cord ; sp.n., spinal nerve ; thai., thala- 

 mencephalon ; S, 4, third and fourth ventricles ; II.-V., VIL-X., cranial nerves. 



B, The brain of a dogfish, in ventral view, cer., cerebrum ; inf., return limb of 

 infundibulum, sometimes regarded as the pituitary body ; l.i., lobi inferiores ; 

 m.o., medulla oblongata ; olf.l., olfactory lobe ; olf.o., olfactory organ ; op., 

 ophthalmic branches of fifth and seventh nerves ; sp.c., spinal cord ; s.v., lateral lobe 

 of saccus vasculosus ; s.v'., median lobe of the same; II. -X., cranial nerves. 

 (From Borrsdaile.) 



