3^8 



THE BRAIN OF THE TIGER SALAMANDER 



the same plane. The arrangement of the fascicles of nerve root fibers is indicated. Neuron 1 

 is in synaptic relation with all components of these cranial nerves. Neuron 2 makes its chief 

 connection with visceral-gustatory fibers of the f. solitarius and less intimate connection with 

 vestibular and trigeminal fibers. Neuron 3 connects only with root fibers of the trigeminus. 

 Neuron 4 connects with the trigeminus and also with the reticular formation and motor zone. 

 Similar elements have been seen to connect also with fascicles of the VIII and other nerve 

 roots. Axons of all these types decussate in the ventral commissure and may ascend in the 

 general bulbar lemniscus. The axon of neuron 2 divides, one branch ascending in the secondary 

 visceral tract {tr.r.a.) of the same side and the other crossing to the opposite side. Some similar 

 neurons connect only with the f. solitarius and have unbranched axons entering tr.r.a. only. 

 Numberless permutations of the various types of connection here shown have been observed. 



olfoctory bulb 

 fasc. post-olfact. 



erebelL 



Figure 10. — Diagram of the chief aflFerent connections of the body of the cerebellum and 

 of the brachium conjunctivum seen as projected on the median section of the brain (chaps. 

 iv and xii). X 18. The more lateral vestibular connections are not drawn. The outline is that 

 of figure 2C, and dotted lines mark ventricular sulci and the boundaries of the chief sub- 

 divisions of the brain wall. 



Figure 11. — Diagram of the chief afferent tracts to the tectum (pp. 48, 220). 



Figure 12. — Diagram of the chief efferent tracts from the tectum. Many shorter connec- 

 tions are omitted (p. 223). 



Figure IS. — Diagram of the connections of the mesencephalic nucleus of the V nerve and of 

 some tecto-bulbar and tegmento-bulbar tracts probably concerned with feeding reflexes (p. 

 140). 



Figure H.—DiagTaxn of the chief afferent tracts to the dorsal thalamus and of some other 

 connections of the optic tracts (pp. 49, 236). 



Figure 15. — Diagram of the chief efferent tracts from the dorsal thalamus (pp. 49, 237) 

 and pretectal nucleus (p. 39). 



