448 TH* BB8PIBATOB7 APPASATV6 /.\ W.I.IM/.I/./.I. 



the foetus, and are gradually hollowed in tlio thickness of the bones which 

 concur to form them. They increase during the minimi's lifetime. },\ the 

 thinning of the bony plates inclosing or partitioning them, and particularly 

 by the growth of the superior molar teeth, whose mot-; pmji-ct into these 

 cavities. The formation of th-- inferior maxillary sinus i.s mure tardy tliun 

 the others; though it is not so late as seven or eight years, as the majority of 

 Veterinary Anatomists have asserted. M. Gouhaux has proved that tin- sinus is 

 already present at six .months old ; and in a head which has been fur several 

 years in the museum of the Lyons School, and which belonged to a foal of 

 very small stature, about a year old, this sinus is seen, in its external part, 

 to be already l inches in depth, and 8-lOths of an inch in width. 



FUNCTIONS OF THE SINUSES. Have the sinuses or diverticuli of the nasal 

 cavities the some uses as these cavities? It is probable, although not 

 absolutely certain. There is nothing to prove that they have anything to do 

 with respiration or olfaction ; and it would seem that their exclusive function 

 is to give increased volume to the head without increasing its weight, and 

 in this way to furnish wide surfaces of insertion for the muscles attached 

 to this bony region these cavities being all the more ample as the muscles 

 are large and numerous. 



DIFFERENTIAL CHARACTERS OF THE NASAL CAVITIES IN OTHER THAN SOUPED AMJIAI.S. 



1. Nostrils In the Ox, the nostrils, placed on each side of the muffle, are narrower 

 and less movable than in the Horse. (The superior extremity of the ala is not horizontal ; 

 the inferior is divided into two branches.) 



In the 1'ig, the end of the nose constitutes the snout (roftrum suis), whos anterior 

 surface, piano and orbicular, shows the external orifices of the nostrils. This snout, a 

 veritable tactile organ employed by the animal to dig np the ground, is covered by a 

 dark-coloured skin, kept damp by a humid secretion, like the muffle of the Ox. It lia< 

 for a base the scoaping-bone, a particular piece situated at the extremity of the nasal 

 septum, and enveloped by a layer of cartilage which extends around the nostrils. It i- 

 easy to distinguish two symmetrical halves in this bone, which evidently n pn * nt tin- 

 two cartilaginous pieces in the nose of Solipcds. 



In the Dog, the end of the nose forms a salient region, which is loughened, nuked, 

 usually dark-coloured, damp, and sometimes divided by a median groove ; in this region 

 the nostrils are pierced, their form resembling two commas opposed to each other by their 

 convexities. The cartilaginous framework sustaining these orifices is not oompoaed of 

 separate pieces, but is only a dependance of the median septum and the appendages of 

 the turbinated bones. 



The same considerations apply to the nostrils of the Cat. with the exception of the 

 colour of the integument, which is nearly always of a rosy hue, like the mucous surfaces. 



2. Nasal Cavities. The nasal fossae of the Ox, Sheep, and Goat are distinguished by 

 the presence of a third turbinated bone the olfactory ant mm, and by the communication 

 existing between them, posteriorly, above the inferior border of the vomer. We have 

 already seen that in these animals, as in those yet to be mentioned, the camd of Jacobson 

 complete ly traverses the palatine arch. 



In tie Pig, the nasal fosste are long and narrow. They are, on the '.i,nai\. \ny 

 short in the Dog and ('at, and the internal cells of the turbinated bones, remarkable 

 for their number and complexity, all communicate with the projx>r na.-al lbss;e, without. 

 concurring in the formation of the sinuses. 



3. Sinuses. In the Or, the frontal sinuses are prolong* d into the bony cores \\hich 

 support the horns, and into the purietal and occipital bones; they therefore envelop, in 

 a most comphte manner, the anterior and supc rior part of the cranium, and form a 

 double wall to this bony receptacl". They are extremely divertioulated, and do mi 

 communicate with those of the great maxillary l*>nes. They usually open, on each side, 

 into the nasal cavilies by four apertures piem d at the base of the great ethmoidal cell. 

 According to Girard, three of these orifices lead to special oi>mpaitmei t-. i olati '1 from 

 one another, and grouped around the orbit : in consequence of which tin Be divertindi of 

 the frontal sinuses are designated the <,,-lnt<il xi'mme*. 



This author has denied the presence of fjjienoidal fiiitiwx; but they exist, although 

 small, and are in communication with the preceding. 



