CHAP, vi.] THE CAT'S ALIMENTARY SYSTEM. 1GO 



with its lips, jaws, teeth, tongue, palate, fauces, and salivary or 

 spittle glands. 



Next follows the part immediately behind the mouth, called 

 the pharynx, which opens into the gullet or oesophagus, which 

 perforates the diaphragm and leads into that dilated chamber the 

 stomach. To this immediately succeeds the small, and afterwards 

 the large, intestine with a blind off-shoot, the ecccum, at their point 

 of junction the whole terminating by that part of the canal which 

 is called the rectum. Annexed to the canal (pouring fluids into it 

 of great importance to the alimentary function) are the pancreas and 

 the liver, and that part of this whole complex system of organs 

 which is behind the diaphragm, lies suspended in the abdominal 

 cavity by a delicate and very complexly-folded membrane, the 

 peritoneum. 



As we have already seen * in the second chapter, the skin which 

 is reflected inwards at the mouth, nostrils, and other body apertures, 

 assumes a soft and delicate texture with a moistened surface, and is 

 known as mucous membrane. We have also seen that the whole of 

 the alimentary tube, and the structures opening into it, are lined by 

 this membrane. The epithelium, which everywhere invests its 

 surface, may be of the columnar form (as in the stomach and 

 intestine), or spheroidal, as in the linings of the alimentary glands. 

 Its corium may contain abundant connective tissue (with many 

 elastic fibres), as in the gullet, or there may be but little, as in tbe 

 walls of the stomach. It may be so richly supplied with minute 

 blood-vessels, immediately beneath the basement membrane, as to 

 seem almost made up of them, while its deepest layer often consists 

 of non-striated muscular fibres. It is also richly supplied with 

 nerves, but their number varies greatly in different regions, as does 

 the sensibility of the parts. 



As to the form and nature of the prominences villi, papillae, 

 &c. which beset its surface, they also are very different in different 

 parts of the alimentary tube. 



7. A fluid, named MUCUS, is almost universally present where 

 mucous membrane exists, and gives its name to that membrane. 

 It is an alkaline or neutral secretion, viscid, colourless, and clear 

 or slightly turbid. It consists mainly of water, but has from 4 to 

 6 per cent, of solid matter, and contains corpuscles. Its special 

 constituent is an albuminoid substance named mucin, which is the 

 cause of its viscidity. Mucus is formed by the epithelial cells of 

 mucous membrane, but especially by certain branching or "race- 

 mose'*' glands. Its use is to preserve the moisture of the membrane, 

 and also to protect it from the dissolving action of the various 

 digesting fluids. It doubtless also helps the senses of taste and 

 smell, partly by preserving the moisture of the surface of the organs 

 of those senses ; partly by helping to dissolve the various sapid 

 matters. 



* See ante, p. 25. 



