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THE NASAL BONES. 171 





tion of the nasals ; for the cavity enlarges considerably upward, aud is 

 occupied chiefly by the ethmoid bone, which, having the greater portion 

 of nervous pulp spread on it, seems to have most to do with the sense of 

 smell. 



The nasal bones of the dog are essentially different from those of the 

 horse, cattle, and sheep. They commence, indeed, as high up in the face 

 as those of the horse, their superior extremities being opposite to the 

 lachrymal gland ; but that commencement is an apex or point varying 

 materially in different breeds. They form, altogether, one sharp projection, 

 and are received within lengthened processes of the frontal bone on either 

 side. In some breeds these processes extend nearly one-third of the length 

 of the nasals. 



The superior maxillary (3.3.) takes the situation of the nasal (2.), 

 pushes the lachrymal bone (4.) out of its place, and almost annihilates it, 

 reaches the frontal bone (7.) and expands upon it, and forms with it the 

 same denticulated suture which is to be seen in the nasal. The action of 

 the muscle between these bones, and for the development of which all this 

 sacrifice is made, is exceedingly powerful. The strength of this muscle 

 in a large dog is almost incredible : the sutures between these bones must 

 oossess corresponding strength ; and so strong is the union between them, 

 ~hat, in many old dogs, the suture between the superior maxillary and frontal 

 \iones is nearly obliterated, and that between the nasal and frontal maxil- 

 . ary quite effaced. 



As the nasal bones proceed downward they become somewhat wider. 

 They unite with a long process of the anterior maxillary for the purpose 

 of strength, and then terminate in a singular way. They have their 

 apexes or points on the outer edge of the bone ; and these apexes or 

 points are so contrived, that, lying upon, and seemingly losing them- 

 selves, on the processes of the anterior maxillary, they complete, supe- 

 riorly and posteriorly, that elliptical bony opening into the nose which 

 was commenced by the maxillary anteriorly and inferiorly. The nasal 

 cavity of the dog, therefore, and of all carnivorous animals, terminates by 

 a somewhat circular opening, more or less in the form of an ellipse. 

 This bony aperture varies in size in different dogs, and, as we should ex- 

 pect from what we have seen of the adaptation of structure to the situation 

 si nd wants of the animal, it is largest in those on whom we are most depen- 

 dent for speed and stoutness. 



The olfactory, or first pair of nerves, have a double origin, namely, 

 from the corpus striatum and the base of the corpus callosum. They are 

 prolongations of the medullary substance of the central portion of the 

 brain. They are the largest of the cerebral nerves. Their course is 

 xceedingly short ; and they have not a single anastomosis, in order that 

 the impression made on them may be conveyed undisturbed and perfect to 

 the brain. 



The olfactory nerve is a prolongation of the substance of the brain, and 

 i<; abuts upon the cribriform bone, of which mention has been made. I 

 \ ill not speak of the singular cavities which it contains, nor of their 

 f mction; .this belongs to the sensorial system: but its pulpy matter has 

 already been traced to the base of the ethmoid bone, and the under part 

 of the septum, and the superior turbinated bone. Although we soon lose 

 it in the mucous membrane of the nose, there is little doubt that in a more 

 filmy form it is spread over the whole of the cavity, and probably over all 



