212 



ANATOMY OF VERTEBRATES. 



side of the proboscis, and is intimately connected with the c orbi- 

 cularis oris/ d d\ e is the zygomatic, f the depressor anguli oris, 

 g the buccinator. 1 The external nose of the Rhinoceros is com- 

 bined with the upper lip and prolonged in a minor degree, but 

 with a like arrangement of muscles, for prehensile purposes. 

 The nose of the Horse is chiefly peculiar for the power of the 

 dilating and contracting each nostril, such movements being sub- 

 served by a lateral semilunar 

 cartilage, fig. 156, k,; by a de- 

 pression or fold of contiguous 

 skin, called e false nostril ' in 

 Hippotomy, and by the homo- 

 logies of the muscles of the 

 combined nose and lip of the 

 Tapir. In fig. 156, a is the 

 ( levator rostri ; ' b is the ( re- 

 tractor labii alreque nasi;' c is 

 the muscle called ( transversus 

 nasi,' in Hippotomy ; e is the 

 zygomaticus; f marks the in- 

 sertion of a muscle, ' pyrami- 

 dalis ' of Hippotomy, which 

 arises by a slender tendon from 

 the maxillary, and gliding be- 

 neath the labial part of b, ex- 

 pands to be inserted, fleshy, into 

 the outer border of the nostril 

 and contiguous skin-folds. 



The Horse is remarkable for 

 the size of the rhinencephalon 

 and the extent of the cribriform 

 plate transmitting its nerves to 

 the nose : they pass upon a 

 series of about ten short longitudinal folds directed forward and a 

 little downward, forming the ( ethmoidal labyrinth' of Hippotomy, 

 the upper larger division being the ' ethmoturbinal ; ' a longer, 

 larger, more simply disposed plate, attached to both prefrontals 

 and nasals, and chiefly descending from the latter bones, forms 

 the ( nasoturbinal : ' beneath this is the c maxilloturbinal,' of 

 about the same vertical extent, and almost the same length. The 

 bony septum contributed by the coalesced prefrontals, forms, 

 superiorly, about one-fourth of the general partition : the vomer 



1 xciii. pp. 20-26. 



Muscles of nostrils and upper iip, Horse. 



