174 THE CAT. [CHAP. vi. 



The buccal glands are small glandular aggregations, each aggrega- 

 tion opening by various minute orifices into the mucous membrane 

 of the mouth. 



The secretion of all these glands constitutes the SALIVA, which is 

 a clear, alkaline fluid, consisting mainly of water, but containing 

 nucleated corpuscles, a peculiar albuminoid substance called salivin, 

 or ptyalin t and a minute quantity of sulphocyanide of potassium. 



This secretion is poured out as it is formed, and its flow is accele- 

 rated by the contraction of the cheeks and tongue. The secretion 

 is stimulated by the presence of food in the mouth, and even by the 

 sight of it. 



The action of this fluid on the food is, first, to soften it and dis- 

 solve what is soluble, including all its crystalloids. It has no action 

 on the albuminoid or gelatinoid substances, nor on the fats ; but it 

 tends to convert starch (at the ordinary temperature of the inside of 

 the mouth) into grape-sugar, thus changing a colloid into a crystal- 

 loid, and so rendering the starch soluble and capable of undergoing 

 absorption and assimilation. This action, however, is slow and 

 feeble in the cat. It is the ptyalin which has this power, which it 

 seems to exercise simply by the stimulating action of its presence and 

 contact ; for if it is precipitated by alcohol, filtered, and then re- 

 dissolved, it will quickly transform as much as 2,000 times its 

 weight of starch into sugar. 



The food having been sufficiently bitten, it is thrust backwards by 

 the tongue through the isthmus faucium. While it passes, the velum 

 palati is raised, and so guards the posterior nares from the intrusion 

 of the food, and the backward motion of the tongue depressing the epi- 

 glottis, while the food passes over it, guards the entrance of the 

 windpipe against the entrance into it of any alimentary matter. 



11. Immediately behind the isthmus faucium is a conical cavity, 

 wider towards its upper part, and more contracted below. This is 

 the PHARYNX. It rises up behind the mouth and posterior nares to 

 the base of the skull, and forms the summit of that canal which 

 leads down from the mouth to the stomach. It consists of the 

 pharyngeal muscles already described, with a lining of fascia and 

 mucous membrane, together with vessels, nerves, and arcolar tissue. 

 It is attached above to the basi- sphenoid and petrosals, and to the 

 basi-occipital by a fibrous membrane, which passes down between 

 the recti antici muscles. It is loosely connected behind with the 

 fascia, investing the pre- vertebral cervical muscles, and laterally 

 with the muscles attached to the hyoidean anterior cornu. In 

 front, it is connected with the pterygoids, the hyoid apparatus, and 

 the larynx. 



There are seven openings into the pharynx. These are : the two 

 posterior nostrils ; and external to these, the two Eustachian tubes ; 

 in front, the mouth ; and below it, the larynx ; while inferiorly, the 

 pharynx opens into (being continuous with) the oesophagus. Its 

 mucous membrane is beset throughout with simple glands, while 

 racemose glands are numerous in its upper part. 



