584 SPECIAL PHYSIOLOGY. 



tion, characteristic of these animals. The crude food, when first swallowed, 

 descends in largish masses, which force open the borders of the oesophageal 

 groove, and so escape into the paunch. Water, doubtless, is conducted along 

 that groove into the honeycomb, or so-called water-bag, but it also partly 

 escapes between the margins of the groove, and so enters the paunch, where, 

 in the camel tribe, it is received into the system of water-cells there situated. 



The food, partially masticated and insalivated, lubricated with mucus, and 

 mixed with water and the juices of the paunch, undergoes maceration in that 

 cavity, and also probably enters the honeycomb, in which it is further watered. 

 Now, moulded by muscular action into small masses or pellets, either in the 

 cells of the honeycomb bag, or by the oesophageal groove itself, it is propelled 

 into the oesophagus, and thence, by an anti-peristaltic action, into the mouth. 

 The soft and small pellet is there deliberately remasticated and insalivated, 

 and is thus reduced to a semifluid pulp, which again passes down the oesoph- 

 agus, and the margins of the oesophageal groove being now closed by mus- 

 cular contraction, so as to form a complete tube, the semifluid mass is this 

 time transmitted into the third stomach, or manyplies, from which it cannot 

 return. Here it is brought into contact with a large surface of mucous mem- 

 brane, loses much fluid, and soluble saccharine and other substances, and is 

 then passed on to the rennet-bag, for the digestion of the albuminoid matters. 



The precise mode of action of the borders of the oesophageal groove and 

 other parts, is not known. Some suppose that the animal conveys the food or 

 drink, instinctively or voluntarily, either into the first or second stomach, or 

 else into the third. But according to another view, the process is partly a 

 reflex act, and partly mechanical. In every act of deglutition, the borders of 

 the oesophageal groove are believed to be approximated by a co-ordinated mus- 

 cular act. When the food or fluid swallowed is large in mass or quantity, it 

 is supposed to overcome the muscular action, and so to pass, if solid, into the 

 paunch, and, if fluid, partly also into the honeycomb ; but if the material 

 swallowed be semifluid or fluid, and in moderate quantity, it is suggested that 

 it may be conveyed along the temporary tube into the manyplies (Flourens). 

 In the act of sucking, the milk is said to pass at once into this cavity, on 

 account of the small quantity swallowed at a time. It is not certain whether 

 the regurgitated pellets are moulded in the cells of the honeycomb bag itself, 

 or in the oesophageal groove; nor whether the pellet is introduced into the lower 

 end of the oesophagus, by the contraction of the sides of the groove, or by that 

 of the reticulum itself. Though reflex, and probably excited by the food as 

 a stimulus, and, therefore, not volitional, these movements of the ruminant 

 stomach and oesophagus may be in some extent controllable by the will. 



In the Pachydermata, the stomach is more simple. Thus, it is elongated, 

 and possesses a long cardiac pouch in the elephant and rhinoceros, but in the 

 former, it presents numerous internal transverse folds. The hippopotamus 

 has two cardiac pouches, opening widely into the rest of the stomach; in the 

 tapir and hyrax, this organ forms two cavities. In the pig the stomach resem- 

 bles externally that of Man, though the cardiac end is more projecting, and a 

 considerable extent of the lining membrane, near the oesophageal opening, is 

 covered with a thick epithelium. In the peccary, still more of the cardiac por- 

 tion is lined by a dense epithelium. 



In the Solipeds, the stomach is rounder, the oesophageal and pyloric openings 

 are near to each other, and the cardiac portion of the organ is lined by a thick 

 epithelium, which terminates by a dentated margin. 



In the Rodentia, the stomach is also marked oft' into a cardiac and pyloric 

 portion, often indicated by an external constriction ; the cardiac part is lined 

 by a thick epithelium, and the pyloric end by a soft, glandular, mucous mem- 

 brane. In the beavers, and some other species, the stomach has glandular 

 crypts and caeca, the use of which is not known. 



The Marsupials, whether carnivorous or herbivorous, have usually a simple 

 somewhat elongated stomach, sometimes provided, like that of the beaver, 

 with numerous crypts. In the kangaroo, the stomach is of remarkable length, 

 being as long as the body ; its middle portion is sacculated, and marked by 

 three longitudinal muscular bands, somewhat like the colon ; it has three com- 



