332 STRUCTURE OF THE sJaEEP. 



the animal, arid are in keeping with the powerful seminal 

 powers possessed by the ram, and which enable him when 

 full grown to serve properly eighty ewes or upwards. 



TilE CONTENTS OF THE CHEST. 



The mouth in the horse is almost entirely devoted to the 

 office of mastication. It is separated from the cavity of the 

 nostrils by a loose fleshy membrane called the velum palati, 

 which is conflned to the bone above by a semicircular bor- 

 der, and falls downwards and backwards so as to prevent, in 

 a natural state, any communication between the windpipe 

 and the mouth. The sheep likewise possesses this velum 

 palati, but it is not so long, and therefore permits this animal 

 to respire through the mouth as well as the nostrils. The 

 importance of this construction is seen in the process of ru- 

 mination, and also accounts for the Ijorse vomiting through 

 the nostrils, on those few occasions when this animal has 

 been known to vomit. The nostrils, however, are the prin- 

 cipal channel through which the air passes to and from the 

 lungs. Their entrance is comparatively small and confined ; 

 the sheep does not require so extensive a supply of air as 

 other animals that are called upon to make considerable ex- 

 ertions. The cavity of the nostrils is divided into two com- 

 partments by a thick cartilaginous substance, termed by 

 anatomists the septum nasi, fixed to the nasal in front, and 

 behind to the maxillary bones. This cartilage, as well as 

 the other parts of the nostrils, is lined by a fine delicate 

 membrane which secretes a mucus for its protection. It is 

 indeed an inflammation of this membrane which constitutes 

 a catarrh or cold, and an increase of its natural mucous se- 

 cretion is the discharge from the nose which is visible in 

 this disease. This membrane is called the Schneiderian, 

 from the name of its discoverer, as well as the pituitary, and 

 it is endowed with a high degree of sensibility, which it de- 

 rives from an abundant supply of sensitive nerves ; it is also 

 the principal seat of the sense of smelling, and for this pur- 

 pose the nerve devoted to this function is spread out on its 

 surface. This membrane also covers four curious bones, 

 thin and gauze-like in their structure, and rolled up like a tur- 

 ban, so that they are termed turbinated, and attached to the 

 chambers of the nostrils. These greatly extend the surface 

 on which the nerve of smell is diffused, and consequently 



