344 



snout of the mole is naked. It is this part of the head that the 

 mole utilizes in digging its burrow. Hoggan ('83)^ suggests that the 

 hairs on the snout of the mole have been torn out so often that, in 

 the course of time, they have become suppressed. From an exami- 

 nation of the animals studied it has been found that, as a rule, those 

 animals with numerous well developed snout vibrissae have small 

 protuberances in the cheeks. The common rat, for example, has nu- 

 merous vibrissae in its snout, and, as has been shown, the organ in 

 question is meagrely developed, there being but three vibrissae. The 

 snout of the white-footed mouse, likewise, is supplied with an abun- 

 dance of these tactile hairs, while in the protuberance there is but 

 a single vibrissa. The mole, on the other hand, with no vibrissae at 

 all in its snout, has in the cheek a well developed protuberance con- 

 taining five vibrissae. 



Innervation of the Protuberance in the Mole. 

 A dissection of the head of the mole (Fig. 5) shows the inner- 

 vation of the protuberance, the larger branches of the mandibular 

 nerve, and some of the adjacent muscles, bones, and foramina. 



1 p Y 



pm 



4 



m 7 X658BMLA HD 

 Fig. 5. Mandibular division of the trigeminus. 

 Fig 5. Mandibular division of the trigeminus. X 5. ^, n. alveolaris inferior; 

 .äJS, n. auriculotemporalis ; 5, n. buccinatorius ; D, n. mandibularis ; e, external au- 

 ditory meatus; if, branch of n. alveolaris inferior to m. mylohyoideus and digastri- 

 cus; h, n. linguaiis; M^ n. massetericus, m, mandible: N. auricular branch of n. 

 auriculotomporalis; or, foramen ovale; P, protuberance; T. N, temporal nerve; X, 

 portion of the temporal nerve distributed to the buccinator muscle; Y, nerve supp- 

 lying the protuberance; z zygomatic arch; 1, ni. temporalis; 2, m. occipitofrontalis; 

 5, m. clavotrapezius; 4, m. stylohyoideus; 5, m. buccinator; 6", m. digastricus; 7, m. 

 mylohyoideus; S, m. masseter. 



1) Hoggan, George and Frances 1883. On Some Cutaneous Nerve Ter- 

 minations in Mammals. Journ. Linn. Society. Vol. 16, pp. 546 — 593. 3 PI. 



