506 



ANATOMICAL TECHNOLOGY. 



1377. PROVISIONAL PHYSIOLOGICAL ARRANGEMENT OF THE CRANIAL 

 NERVES. (Slightly altered from Dal ton, A, 447.) 



A. NERVES OF SPECIAL SENSE, LACKING GENERAL SENSIBILITY. 

 I. Olfactorii. 2. Opticus. 3. Auditorius. 



B. MOTOR AND SENSORY NERVES COMPARABLE WITH MYELONAL NERVES. 



1378. Dalton recognizes two great divisions, the nerves of spe- 

 cial sense and ordinary motor and sensory nerves. Since some of 

 the latter also possess special sensibility, the former may perhaps 

 be characterized as nerves of special sense which lack general 

 sensibility and have no ganglia. 



The other and larger division includes nerves which are anatom- 

 ically and physiologically distinguishable into two groups, cor- 

 responding respectively to the dorsal and ventral roots of 

 myelonal nerves. Three of these bear each a ganglion, like that 

 upon the dorsal root of a myelonal nerve, and are, at their origin, 

 exclusively sensitive. The others apparently lack ganglia and are 

 functionally motor. 



But while the foregoing Arrangement is at least convenient and 

 serves to impress upon the mind of the student the probability 

 that, as the " medulla " is a modification of the myelon, so some at 

 least of the cranial nerves are modifications of the myelonal type, yet 

 sight should not be lost of certain ascertained or probable facts of 

 Embryology and Comparative Anatomy which are not in full accord 

 therewith. 



These facts and considerations are admitted by Wyman and Dal- 

 ton, and others are presented in the compendium s of Huxley, A, 66-71, 



