DIGESTION. 85 



ing their experiments, and have detailed all their proceedings, 

 while the French writers merely give results, and appear to have 

 bestowed far less pains, I must be excused for merely mentioning 

 their work. e 



The inspection of living animals shows, that, during chymifi- 

 cation the mucous membrane of the stomach, and during chy- 

 lincation that of the small intestine, becomes strikingly red ; and 

 if an animal is killed during either process, this redness is seen 

 in the corresponding portion of the coat. f 



e Recherches Physiologiques et Chimigues pour servir a VHistoire de la Digestion. 

 Paris, 1825. 



An immense number of curious facts respecting different articles of food, and 

 many points on the subject of digestion, will be found in the German work, and 

 a good history of opinions in the French. 



f Andral, Precis d' Anatomie Pathologique, t. ii. P. i. p. 6. 



In granivorous birds the food passes into the crop, and from this into a second 

 cavity, from which it enters the gizzard, a strong muscular receptacle, lined by 

 a thick membrane, in which, instead of having been masticated, it is ground by 

 means of pebbles and other hard bodies swallowed instinctively by the animal ; 

 hence true salivary glands do not exist about the mouth of birds, but abound in 

 the abdomen, opening into the lower part of the oesophagus and into the crop and 

 gizzard. In carnivorous birds, the gizzard is soft and smooth. The fluids of 

 both crop and gizzard contain a free acid, according to Tiedemann and Gmelin, 

 which is the muriatic or acetic. 



Some graminivorous quadrupeds with divided hoofs have four stomachs, into 

 the first of which the food passes when swallowed, and from this into the second. 

 It is subsequently returned by portions into the mouth, chewed, and again swal- 

 lowed, when, by a contraction of the openings of the two first stomachs, it passes 

 over them into the third, and from this goes into the fourth. The process can be 

 delayed at pleasure when the paunch is quite full. Some birds and insects also 

 ruminate. The same chemists found the fluids of the two first stomachs alka- 

 line, and of the third and fourth, acid. The stomachs of some insects and cms- 

 tacea contain teeth. Some zoophytes are little more than a stomach, the food 

 taken into it being chiefly dissolved and absorbed, and the refuse expelled at 

 the orifice by which it had entered : others have several openings on the surface 

 leading by canals that unite and run to the stomach, a structure called by 

 Cuvier, mouth-root. In regard to vegetables, it is not the whole root which ab- 

 sorbs, but the minute fibrous prolongations, which are called spongioles. Some roots 

 are also reservoirs of nourishment. Between the most distinct kinds of stomach 

 we see numerous intermediate varieties. The cardiac half of the interior of the 

 stomach of the horse, for example, is covered by cuticle, and appears merely 

 recipient, while the pyloric half is villous and digestive ; and the state of the con- 

 tents in each half is, therefore, very different : a link thus existing between such 

 stomachs as the human and the ruminating. 



