DIGESTIVE SYSTEM. 39 



two pairs of tolerably conspicuous cornua. In the Ruminantia, the 

 body represents a small bow, and the anterior cornua are united 

 with a very long styloid process, a peculiar bone in itself. The 

 structure in the Horse is similar, only the body is larger, and the 

 anterior cornua consist of single pieces ; in both orders, as in the 

 Pachydermata, the posterior cornua are anchylosed to the body, and 

 very short, as in the Elephant and Rhinoceros especially. The pos- 

 terior cornua are generally the longest in the Rodentia, and particu- 

 larly in the Marsupiata, among which they are least in Didelphis, 

 and their pieces are elongated and slender, as is also the case in the 

 Carnivora. In most Apes the anterior cornua are elongated, or as 

 long as the posterior, and simple. In the Orangs the anterior cornua 

 are small, as in Man, in whom they are very small, and far surpassed 

 in size by the posterior pair. In the howling Apes (Mycetes), the 

 body is expanded into a very large, thin-walled, bony bladder, in, 

 which the voice formed in the windpipe resounds, and is thus ren- 

 dered so remarkably loud. 



The manducatory, lingual, and hyoid muscles present themselves 

 generally in the Mammalia, as in Man, with, however, a number 

 of minor differences. Thus it is only in the higher orders that the 

 digastric muscle is truly double-bellied, and is, even in the Apes, 

 not generally perforated by the stylo-hyoideus. The omo-hyoideus 

 is very frequently wanting, next to it, the stylo-glossus, and stylo- 

 hyoideus. As a rule, there is developed a peculiar masto-hyoid 

 muscle, which draws the styloid bones powerfully backward. 



The (Esophagus is short and very wide in the Cetacea, so also in 

 the Carnivora and Makis. It is otherwise, as a rule, long and nar- 

 row, and in many Rodentia, as the Hamster, passes far beyond the 

 slit in the diaphragm. It has frequently a thick epithelium, and its 

 inner surface is longitudinally plicated, but it is rarely, as in Didelphis, 

 provided at its inferior extremity with valvular spiral folds : as a rule, 

 it passes to the stomach without any valve. In the Horse, however, 

 there is developed a more or less large sickle-shaped fold, which can 

 close the cardia, and prevent the return of food, so that the Horse 

 can not vomit. 



The Stomach exhibits remarkable diversities. In the greater 

 number of Mammalia it is simple, as in Man and in most Apes, 

 where it is, however, mostly rounder than in Man, and in the Makis, 

 has a considerable ccEcal dilatation. The slender Apes (Semno- 

 pithecus) form a striking exception ; here the left half forms a 

 large cavity many times constricted, while the right is long, narrow, 



