144 



OF THE ANTERIOR CAVA. 



vessel, the valves not acting ; but when the animal feeds 

 from the ground, and the blood has to ascend against 

 gravity, the valves are of service, and come into full ope- 

 ration. 



FIG 17. 



THE VEINS OF THE HEAD AND FACE. 



a, The jugular. 



b, The submaxillary. 



c, The labial. 



d, The facial. 



e, The tempoi'al. 



/, The sinus, or pouch, within the masseter 



muscle. 

 g, The posterior masseter. 

 h. The parotideal. 

 i. The auricular. 

 j, The occipital. 



Of the origins of veins, one is from arteries, which 

 have previously terminated in capillaries ; and likewise 

 from large cavities or sinuses. Veins are furnished with 

 arterial blood from the vasa vasorum, given off by the 

 nearest arteries ; which blood is returned by minute venae 

 venarum into the nearest veins. The blood within the 

 veins is returned' to the heart in a regular flow ; at least no 

 pulsation has ever been satisfactorily detected within them. 



OF THE ANTERIOR CAVA. 



All venous trunks eventually terminate in the anterior 

 and posterior cavce {Fig 1 8 . «, k) ; in both of which, other 

 veins also terminate. In this detail we shall commence a 



