Herrick, Medulla Oblongata of Fishes. 405 



The ordinary feeding reflexes of Ameiurus are generally total 

 reactions of a simple type, but involving the use of most of the 

 striated muscles of the body. Contact of a barbel or other sensi- 

 tive part of the outer skin with a morsel of food is follow^ed by a 

 turning of the body in the direction of the food and the movements 

 of the jaw^s and pharynx necessary to seize and swallow it. The 

 first movement involves practically the entire body musculature 

 and probably requires the discharge of nearly all of the peripheral 

 neurones of the somatic motor type except the eye-muscle nerves. 

 And if the gaze of the fish is simultaneously directed toward the 

 food object, these motor nerves, too, must be brought into play. In 

 a similar way, the movements of seizing, mastication and swallow- 

 ing require the discharge of nearly all of the peripheral neurones 

 of the head belonging to the specialized visceral motor system — 

 motor V nucleus for the muscles of the jaw and operculum, motor 

 VII nucleus for the muscles of the hyoid and its derivatives, and 

 motor IX and X nuclei for the muscles of the gills and oesophagus. 



In the spinal cord of fishes we know from the figures of Retzius 

 ('93), VAN Gehuchten ('95), Martin ('95), and others, that the 

 ventral horn cells, which innervate the somatic muscles, send their 

 dendrites out to ramify widely in the region of the lateral and 

 dorso-lateral funiculi and adjacent formatio reticularis (funic- 

 ulus lateralis proprius). Our problem here, then, is to determine 

 the relations of the two primary sensory centers in question to each 

 other and to these longitudinal pathways of the spinal cord. 



Similarly in the oblongata, the nuclei of the peripheral motor 

 nerves mentioned above are known to receive their innervation 

 chiefly by way of the formatio reticularis alba et grisea {cf. Cajal, 

 '96, and Herrick, '05) and we have now to learn the relations of 

 the primary gustatory and tactile centers to this structure and its 

 derivatives. 



In the teleosts here examined all of the tactile (general cutaneous) 

 nerves of the head enter the brain by two roots, the sensory trigem- 

 inus root and the general cutaneous root of the vagus. The latter 

 is probably always present in teleosts, though often so small as to 

 be distinguished with difficulty. In Prionotus it is very large. 

 Upon entering the oblongata, the sensory trigeminus root turns 

 caudad as a whole to constitute the spinal V tract. There is no 

 appreciable "chief" sensory nucleus at the level of entrance of the 

 nerve, nor have I been able to demonstrate in teleosts a mesen- 



