NERVES OF REPTILES. 



309 



to form the 'ramus ventriilis,' v. The filament of the ventral 

 root sent to the ramus dorsalis of the succeeding nerve perforates 

 the lower division of the dorsal root of its own ner^'e. 



Thus each spinal nerve forms a ' ramus dorsalis,' fig. 205, lo, 

 and a ' ramus ventralis,' ib. 8 ; the ramus dorsalis includes a 

 sensory filament of its own nerve, and a motory filament of the 

 antecedent ner^'c : the ' ramus ventralis ' is fijrmed by a motory 





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and a sensory filament of its own nerve ; both rami ' A'enti-ales ' 

 and ' dorsales ' are associated together, and with the vagal and 

 trigeminal nerves through the medium of the great ' nervus 

 lateralis,' fig. 205, i, 8. 



The dorsal roots of the nerves distributed to the free, explora- 

 tory, pectoral rays of the Gurnards, rise from special ganglionic 

 swellings of the cervical portion of the dorsal myelonal columns. 



§ 56. Nerves of Rejjtiles. — The olfiictory nerves are continued 

 in Reptiles, for a greater or less extent, from the rhinencephalon, 

 figs. 188, 191, to the olfactory sacs; the white and grey tracts 

 beneath the proscnceiihalon, fig. 190, p, descrilied as roots of this 

 nerve, belong to the rluncncephalic crura : the true olfactory 

 nerves are less distinct from their centres than in other Ver- 

 tebrates. In the Python, fig. 188, the nerves, i, of equal 

 diameter with their centres, gradually expand, by resolution of 

 their fibres, as they aj^proach the olfactory sacs, ib. d, and are 

 joined by part of the first division of the ' fifth.' The olfactory 



