20 OHFO STATE ACADEMY OF SCIENCE. 



instead of being barely discernable by refined histological methods, 

 as in the human body. And the secondary gustatory path, which 

 in man is totally unknown, is the largest single tract in the brain,, 

 both in the cat fish and in the carp ! 



The primary gustatory center in the medulla oblongata is 

 bilobed, the ''facial lobe," receiving the gustatory fibers from the 

 skin and the "vagal lobe" receiving those from the mouth. From 

 these lobes there is both an ascending and .a descending gustatory 

 path. The latter passes down to the point where the medulla 

 oblongata merges into the spinal cord and there terminates in a 

 special nucleus which is intimately related to the funicular nuclei, 

 a center for tactile sensations. Here the tactile and gustatory 

 stimuli are co-ordinated and a common descending bundle (terti- 

 ary path) passes back into the spinal cord for the body movements 

 necessary to turn toward the food object. The ascending sec- 

 ondary gustatory path extends upward to a big nucleus under 

 the cerebellum, from which tertiary pathways extend forward 

 and downward into the midbrain (chiefly in the inferior lobe),, 

 then backward by a descending path of the fourth order into the 

 medulla oblongata to reach the motor nuclei of the cranial nerves. 



We have already g'one far enough into our analysis of these 

 secondary and tertiary gustatory paths to make it perfectly safe 

 to predict that all of the habitual gustatory reflexes which we have 

 observed in these fishes can be followed anatomically through 

 the brain for their entire extent. And since we have the strongest 

 reasons for believing that the elementary reflex paths are essen- 

 tially similar in mammals and fishes, we expect to find here an 

 important guide for further research in human anatomy. 



So the other sensori-motor systems may be severally investi- 

 gated, beginning the attack in each case with some species low 

 down in the vertebrate series in which this particular mechanism 

 IS highly developed, and then extending the research to higher 

 and lower types. 



We may ultimately hope for a subdivision of the brain which 

 shall be both structural and functional, each organ or pathway 

 being given its function or meaning in the system as a part of tlie - 

 machinery of keeping the body in vital, helpful contact with 

 environing forces. The great morphological "head problems," 

 such as the primitive metamerism and the subsequent marvelous 

 kalaidoscopic changes in structure and function of the component 

 segments, these must all be read through the medium of such an 

 intensive study of these factors upon which all differentiation has 

 in last analysis depended. 



