200 Journal of Comparative Neurology. 



Section 3. — The Central Relations of the Cranial 

 Components. 



Before proceeding with tlie description of the nerves it 

 will be profitable to discuss the terminal relations within 

 the brain of some of the components of the cranial nerves 

 and their probable relation to the spinal components. 

 The motor nuclei can best be described in connection with 

 the several cranial nerve roots to which they give origin; 

 they will, therefore, in this section receive only a brief 

 general treatment. The sensory terminal nuclei are, how- 

 ever, grouped into systems each of which is related to 

 several of the cranial nerves as ordinarily enumerated. A 

 preliminary description of each of these systems, taken as 

 a whole, will assist in the ultimate analysis of the cranial 

 roots, ganglia and rami which are related to them. 



I. — The General Cutaneous System. 



The general cutaneous nerves supply general sensation 

 to the skin without specialized sensory end-organs. 

 Nerves from lateral line organs and from terminal buds 

 are excluded from this system. These nerves correspond 

 in every respect, however, with the cutaneous fibres of 

 the spinal nerves and are serially homologous with them. 



In Menidia this system is represented in the V and X 

 cranial nerves only. Such fibres are said to occur in the 

 IX nerve of other forms — Selachians, Ewart ('89 and 

 '92), Chimsera, Cole ('96, p. 664), and Acipenser, 

 Johnston ('98, p. 585). 



By far the larger part of these fibres arise from the 

 Gasserian ganglion, and these make up the whole of the 

 sensory trigeminus root. They are so intimately joined 

 to the motor V fibres that within the brain it is not possi- 

 ble to separate the two components perfectly, (Fig, 20). 



