Tin: .trr/:M//> OBQAN8 OF r/.s/O.Y. 835 



it passes to the inner surface of the outer wing of the nostril ; there it 

 terminates by an orifice, sometimes two, that looks as if punched out of the 

 infinliriuic. towards the lower commissure, near the point where there is a 

 line of demarcation between the dark colour of the skin, and the rosy tint 

 of tlu- mucous lining. 



" This aperture constitutes the ' nasal outlet ' (egout nasal). 



" The epithelium of the membrane lining the canal is ciliated in its 

 bony, stratified in its nasal, portion. On the surface of the membrane are to 

 be seen the openings of the secretory ducts of some conglomerate glands, 

 which are lodged in the walls of the canaL Throughout its extent, the 

 canal is lined by a continuation of the mucous membrane of the lachrymal 

 sac. In Solipeds, this canal opens on the cutaneous surface at the entrance 

 of the nostrils ; and it therefore happens that in these animals the con- 

 junctiva, with its dependencies, forms a particular mucous membrane, really 

 apart from the great gastro-pulmonary membrane. 



" In the Ass and Mule, the orifice of the lachrymal canal is situated at 

 the inner face of the outer wing of the nostril, and not near the inferior 

 commissure, as in the Horse." F. Lecoq : ' Exterieiir du Cheval,' etc. 



(Sometimes this outlet is double. The lachrymal secretion is not only 

 useful in facilitating the movements of the eyelids over the eyeball, but it 

 \va>lics away dust aud hurtful matter from off the surface of the cornea, 

 keeping the latter clean, moist, and healthy.) 



DIFFERENTIAL CHARACTERS IN THE VISUAL APPARATUS IX OTHER THAN SOUPED 



ANIMALS. 



KSSENTIAL ORGAN OF VISION. In the Ox, the eyeball resembles in shape that of the 

 Horse ; but in small animals, particularly the Dog, it is much more spherical. In Birds 

 it is very convex in front ; its largest diameter is the nntero-posterior. 



r'atic. This is the same in all the domesticated quadrupeds. In Birds, however, it 

 has some curious feature*. Posteriorly, it has for base a cartilaginous layer, covered on 

 both si<li s l.y lilirous tissue; this layer frequently ossities around the optic nerve, where 

 it forms tin: posterior sclerotic ring. Around the cornea, there is the anterior sclerotic 

 rinu,', i-i.injMi-Cil of small bony imbricated scales, capable of moving on each other, and 

 . in^' th<- shape >f the globe of the eye. 



c-.i. --In tli- If'i'i and Cut, the structure of the cornea is similar to that of the 

 Ib.r.-e. ( K'. Hiker Mat. -b tlmt he observed lymphatics in the cornea of a young Cat.) In 

 - <-yi, and 1'iij, th> re are two limitary membranes ; one beneath the epithelium 

 of the anterior fare, hi Itirdt, this limitary memlirane is thickest in front. 



clmroid. In manunifcrs, there are some slight differences in the coloration of the 



ta]>- tinn. Tims, in the its. it is golden green, which becomes blue at the circninten nee; 



in the >'/<'/, it i- a p.ile -"Men green; a gulden yellow in the Cut ; and \vli;te. bordered 



with 1'lne. in tin- l><"i. (It i- al'.-entin tlie Pitj.) In Bird", it is uniformly black ; this 



membrane has also a network <>f non-*tri|>e<l muscular fibres, and, in addition, < 'r<r,n]itnn'i> 



muscle, which ari.-e.- fr-nn ti.e inner fare of tlie os.-eous ring, nnd is i;:-. rt-d int> the 



/. (According to Hassenstein, in rapacious animal- tin -re is. 1 1 hind the 



mi, a layer of eurpux-les composed of lime salts; to this is owing the brilliancy of 



- in tlie ilark.) 



Int. In all animals th<- iri.- is mti.-eulur. In mninmifers. the contractile fibres arc 

 non-striped; in Hint.-, they are stiiped. (In the Ox, it* anterior face has a brighter 

 colour than in the Horse. In the Sherp it is a brownish-yellow ; in the <int Mi;. 1 

 the L>og its colour is a more or le.-.s bright golden-yellow ; in tl.e adult Cut green; and 

 in young anim.ds a bright blue. '1 he pupil ia elliptical in the (>s, as in Sobped- (in 

 the >'//";- and tJiMil it is more elongated) ; in the l),^ it is eircnlur, and, when very 

 much ililat.-d, it is the same in tlie Cut; I. tit. \\ben 



illy, and i iirow as to n-prosent nothing more than a thin perpendicular 



blit. (l.i tli.- /'/;/ it is round. 



There up- no dilFeretnvs woithy uf note in the f.tln-r p.irt." of the 



KSHOBY ORGANS <>K THE VISIAL AM-AICATI >.. 'I'lu nmtur <>rgns are nearly tie 

 in all the nth-r :iniiiial. 



:: it -J 



