THE HORSE. 



93 



stronger in its texture, and, I believe, is 

 both insensible and inorganic. It adheres 

 to the muscular covering by a fine cellular 

 tissue, the extensibility of which gives full 

 play to the latter ; and admits, during the 

 empty or collapsed state of the tube, of the 

 former being thrown into many longitudinal 

 plicce or folds ; as is demonstrated by mak- 

 ing a transverse section of the tube : such 

 appearances result from the contraction of 

 the one coat, and the want of proportion- 

 ate elasticity in the other. Between the 

 two tunics, imbedded amongst the connect- 

 ing cellular tissue, are numerous follicular 

 glands, whose office is to pour forth a mu- 

 cous secretion upon the internal surface of 

 the lining membrane, to render the passage 

 of food along it glib and free from any 

 friction. 



" NASAL FOSSiE.* 



" The nasal fossae are the two chambers 

 or lateral cavities, whose external openings 

 are the nostrils. Their walls or external 

 parietes are almost entirely osseous ; and to 

 the OSSEOUS SYSTEM (page 45) the reader 

 must turn for a description of the manner 

 in which the fossae are formed, and of the 

 bones entering into their formation. But, 

 in addition to bone, they are cartilaginous 

 in their constitution. 



" The cartilages of the nose are five in 

 number: — of which one (the septum nasi) 

 is situated internally ; the other four (enter- 

 ing into the composition of the nostrils) ex- 

 ternally. 



" The septum nasi is the vertical carti- 

 laginous partition interposed between the 

 nasal fossae. It exhibits four borders. The 

 inferior one is received into the groove of 

 the vomer ; while the superior presents a 

 lengthened channel between two elevated 

 edges, into which is admitted the internal 

 crest formed by the union of the nasal 

 bones. Its posterior border is affixed to the 

 ethmoidal plate : its anterior serves to sus- 

 tain the cartilages forming the nostrils. 

 Both its sides are completely covered by the 

 Schneiderian membrane. 



* Hippopathology. 



" Nostrils. — Four in number : two on 

 each side, distinguished by the epithets true 

 and false. 



" The true nostrils are the large, ovoid, 

 and ever-open orifices so conspicuous ex- 

 ternally. They have for the base of their 

 structure four pieces of fibro-cartilage, 

 which are involved in doubfings of the 

 common integument. Each nostril is formed 

 of two flexible alee or wings : a superior or 

 internal one, and an inferior or external. 

 The former is supported by a broad circular 

 cartilaginous plate ; the latter is crescentic 

 in shape, and forms a flexm*e outward, 

 within which is perceptible the orifice of 

 the lachrymal duct. They are attached to, 

 and supported by, the nasal peak and sep- 

 tum nasi. 



" The false nostrils are t^vo fittle pouches 

 or cavities (having the semblance of culs- 

 de-sacs), situated internaUy, above the true 

 nostrils, into which an external opening is 

 found within the commissure formed by the 

 union of the two alse. They are formed 

 out of dupficatures of the skin, which is 

 here tliinner, and finer, and softer in its 

 texture ; and, except at their entrance, are 

 without hair upon their surfaces. Their 

 use is not known. 



" Schneiderian membrane. — The cavity 

 of the nose is not only divided into the two 

 nasal fossae, but each fossa is subdivided 

 into the three meatus (for a description of 

 which, vide page 45). Every part of these 

 cavities and passages is covered by the 

 Schneiderian or pituitary memh'ane. This 

 is a membrane of the mucous class, dis- 

 tinguished for its thickness of substance, 

 for its vascularity, and for its olfactory pa- 

 pillae. It has two surfaces: an exposed 

 or secreting one and an unexposed or ad- 

 herent one. The secreting surface is 

 smooth, and is rendered gfib and shiny by 

 the varnish it derives from the mucous 

 secretion emitted by the numerous small 

 rounded pores everywhere visible in the 

 membrane, but more particularly upon the 

 lower part of the septum, and upon the 

 inferior turbinated bone. This surface 

 exhibits a pale pink blush, the effect of the 



