240 ZOOLOGY. 



on being ruminated or n -masticated descends only to the 

 tliird by means of the o->opha^eal canal, is not an act of intel- 

 ligence, but our purely instinctive, and perhaps even mecha- 

 nical, due to the anatomical disposition of the structures. 

 Food of the size it is when first swallowed, opens mechanically 

 the semi-canal, by which the gullet communicates with the first 

 and second stomachs; but fluids and the remasticated food being 

 much liner, do not effect this, and thus pass on by the canal 

 into the maniplus or third stomach. Rumination is generally 

 ascribed to the second stomach, but it appears more probably 

 due to a combined action of the first and second, which, by 

 contracting, forces the bolus again into the gullet, by which 

 it remounts to the mouth. 



The paunch is of very great size in the adult animal ; in 

 the young, whilst living on the milk of the mother, it is 

 smaller than the rennet, thus showing (?) the influence the 

 food exercises in enlarging the capacity of the organ. 



405. The capacity and length of the intestines are much 

 less in the carnivora than in the herbivora, being in many of 

 the former only three or four times the length of the body ; 

 whilst in the sheep, for example, it is nearly eight times that 

 length. Generally it terminates by a distinct opening; in 

 the ornithorhynchus, however, the anus opens into a cloaca, 

 or cavity, in which terminate also the urinary organs, resem- 

 bling birds in this respect. The salivary glands, the liver, 

 pancreas, peritoneum, and its appendages, resemble the same 

 organs in man. 



406. The more essential differences exist in the apparatus 

 of respiration and circulation; the heart has always two auricles 

 and two ventricles ( 92, Figs. 30, 31) ; the lungs are alwa\ > 

 composed of cellules, which do not allow the air to escape into 

 the other organs of the body, as in birds. The blood is rich 

 in organized matters, and the form of the globules circular 

 ( 81, Fig. 27). 



407. We have already shown that the mammals differ 

 widely from each other in respect of intelligence ^ .'J37) ; 

 and the various instincts bestowed on them by nature to 

 supply the deficiency of a higher intelligence have been 

 already alluded to. It is the class which most interests man, 

 including within it, as it does, so many of our domestic ani- 

 mals ; the horse, ox, sheep, &c. So complete, indeed, have 

 hivn the effects of domesticity over some of these ra< > of 

 animals, that the primitive race seems altogether to have 

 disappeared. The moral as well as the physical characters of 



