CHAPTER XII. 



THE TRIGEMINUS OE FIFTH PAIE OF SERVES. 



Its Xature and the Relation it bears to the Teeth. Its Course in 

 the Horse and in Man. 



THE thread-like nerves of the teeth are derived from 

 the superior and inferior maxillary branches of the 

 trigeminus or fifth pair of nerves. In the horse these 

 branches are four or five times as thick as a ribbon 

 and about five-eighths of an inch wide. The ophthal- 

 mic branch is smaller and shorter, its course extend- 

 ing only from the brain to the eye, while that of the 

 two former extends to the lips, running parallel to and 

 about an inch from the roots of the grinder teeth.* 



The description of the trigeminus and its course is 

 from a lecture by Prof. Youatt to veterinary students, 

 and may be found in "The Veterinarian" for 1834 

 (p. 121). In the first part of the lecture the nature of 

 the trigeminus its double origin and function is 

 expatiated upon, a summary of which is that the sensi- 

 tive and motor roots, are contained within the same 

 sheath ; that the sensitive root is so much larger and 

 its fibrils so much more numerous than the motor that 



* For the preparation of an anatomical specimen showing the 

 general course of the trigeminus, I am indebted to Prof. J. M. 

 Heard, of the New York College of Veterinary Surgeons, 



