234 DIGESTIVE SYSTEM. 



in the other they are wholly free from it. They are not to be re- 

 garded as respiratory organs in the fcetus. It is evident therefore, 

 that the lungs owe their property of hghtness to the air they con- 

 tain ; and, as a further proof of it, if that fluid be by any means , 

 absorbed or pressed from them, and their bulk diminished by col- 

 lapse of the air-cells, like other viscera, they will prove heavier 

 than an equal volume of water : hence it is that the lungs of a 

 horse that has died of hydrothorax, even though they be sound, 

 are of a greater specific gravity than those of one in health. It 

 occasionally happens, however, that these viscera evince, in this 

 particular, the properties of airless lung, while their natural vol ume 

 and general appearance remain the same: there must be present 

 interstitial deposition. 



Bronchial Glands. 



Small, oval-shaped, glandular-looking bodies, situated about 

 the roots of the lungs, adhering more particularly to the bottom of 

 the trachea and the bronchial tubes. They exhibit a dirty French 

 grey hue, interspersed with dark blueish spots, and are about the 

 volume (though this varies much) of a tick-bean. For a long 

 time the nature of these bodies remained obscure : of late, skilful 

 injections have clearly shewn them to be absorbent glands. They 

 possess their capsules, and, when cut open, exhibit a cellular 

 structure. They contain a dark fluid,' which will soil any thing it 

 touches; whose principal ingredient chemists have found to be 

 carbon. 



Section V. 

 DIGESTIVE SYSTEM. 



IN THIS SYSTEM ARE COMPRISED THE MOUTH, TONGUE, 

 SALIVARY GLANDS, PHARYNX, ESOPHAGUS, STOMACH, 

 INTESTINES, LIVER, SPLEEN, PANCREAS. 



OF THE MOUTH. 



IT may be observed here (as prefatory to the description of 

 this pait), that in quadrupeds in general, the facial angle* is one 

 of very considerable obliquity, in consequence of the prolongation 



* The. facial angle is the point at which one line drawn parallel vvith the 

 exterior of the frontal bone is intersected by another extended parallel with 

 the lower border of the inferior maxilla. 



