Art. II. 1 Herrick, Gustatory Paths in Fishes. 103 



B. Long Paths. 



5. The descending secondary gustatory tract arises from the chief gustatory 

 cells of the facial lobe mainly and terminates partly in the inferior secondary gus- 

 tatory nucleus and a smaller part lower down in the spinal cord. This puts the 

 taste buds in the outer skin into very direct relations with the trunk musculature 

 and so provides for the body movements necessary to turn and seize food after 

 its detection by contact with cutaneous taste buds. This inferior nucleus, as 

 stated above, is connected by a rich fibrous plexus with the funicular nucleus, 

 which is the primary tactile coordination center for the skin of the head and 

 trunk. Thus the cutaneous gustatory and tactile impressions may be brought 

 into relation, as required by the physiological evidence that these senses cooper- 

 ate in the localization of food objects. 



6. The ascending secondary gustatory tract arises from the chief secondary 

 neurones of both vagal and facial lobes and terminates in the superior secondary 

 gustatory nucleus located in the lateral wall of the isthmus (the "Rindenknoten" 

 of Mayser). It ends chiefly on the same side, but a part of its fibers cross 

 through the commissure of the secondary nuclei to end in the opposite nucleus. 



The superior and inferior secondary gustatory nuclei are both specializations' 

 of the substantia reticularis grisea. The superior nucleus is especially intimately 

 connected with the motor V nucleus, partly directly and partly through another 

 specialized area termed the substantia reticularis grisea trigemini. It also has 

 connections cephalad with the region of the eye-muscle nuclei and the nucleus of 

 the fasciculus longitudinalis medialis, thus putting the gustatory system into 

 physiological relation with the somatic motor centers. There is also probably an 

 important connection between the superior nucleus and the cerebellum and val- 

 vula cerebelli by way of the nucleus lateralis valvulae. These important mesen- 

 cephalic and cerebellar connections merit much more thorough study. 



7. The chief tertiary gustatory tract arises from cells in the cortical layer 

 of the secondary nucleus, whose dendrites receive the terminal arborizations of 

 the secondary fibers. This tract is heavily medullated and mingles with the 

 tractus lobo-cerebellaris (Edinger) and other vertical tracts connecting with the 

 cerebellum, so that it is difficult to follow it separately. GoLGl impregnations 

 show that its fibers pass ventrad and slightly cephalad to arborize widely through- 

 out the lateral lobule of the inferior lobe (hypoaria, C. L. Herrick) along with 

 others from the forebrain, tectum, etc. This appears to be the chief center for 

 the correlation of olfactory and other higher senses. 



8. The return path for all of these sensory activities of the inferior lobe is 

 the tractus lobo-bulbaris, the dendrites of whose cells of origin ramify widely 

 among the gustatory and other terminals just mentioned. This tract (Mayser's 

 "Nervenfaser-bundel x") passes into the oblongata mesially of and partly enclos- 

 ed by the ascending secondary gustatory tract and along the lateral border of the 

 substantia reticularis grisea, within which its fibers gradually diffuse themselves. 

 Through the medium of this reticular area the descending impulses from the in- 

 ferior lobe come into relation with the peripheral motor neurones of the oblonga- 

 ta and probably also of the spinal cord, thus providing for the most complex re- 

 flexes of which the fish is capable. 



