THE RABBIT. 27 



the middle line by the side of the dorsal aorta, and brings 

 lymph from the whole posterior region of the body and the 

 alimentary canal. It is therefore much larger than the 

 others, and being most conspicuous in the thorax has been 

 called the thoracic duct. Near the anterior end of the 

 thorax it bends round to the left, and after joining the 

 lymphatic trunk from the left side of the neck, opens into 

 the origin of the left precaval vein. The right lymphatic 

 trunk of the neck opens into the corresponding vein on the 

 right side. 



The lymphatics of the alimentary canal (abdominal 

 portion) and mesentery are specially developed and known 

 as lacteals, because they contain (at least in animals fed on 

 a ratty diet) a milky fluid, the chyle. This owes its milky 

 appearance to the presence of abundant minute drops of 

 oil, re-formed out of the soaps and glycerine absorbed in 

 the intestine. As already mentioned (chap, ii., 13) there 

 is a network of lacteals in each villus of the duodenum, 

 and there are others all along the intestine. These unite 

 into larger and larger vessels, with " lymph-glands," some 

 of very great size, set upon their course ; they finally open 

 into the thoracic duct. 



10. The heart of the rabbit (see fig. 59, B) is divided 

 by partitions into four chambers : two anterior thin-walled 

 ones, the auricles, and two posterior ones, the ventricles, 

 both of which, but especially the left, have very thick, 

 muscular walls. The right ventricle and auricle com- 

 municate, and the left ventricle and auricle, but the 

 chambers of right and left sides are absolutely distinct. 

 The veins open into the auricles the three great caval 

 veins (bringing blood from everywhere except the lungs) 

 into the right auricle, the pulmonary veins (bringing blood 

 from the lungs only) into the left auricle. From the 

 auricles the blood passes into the ventricles, from which 

 the arteries arise. The arteries do not, however, come off, 

 as might be expected, from the posterior end of the ventricles 

 they come off from their anterior end, alongside the 

 auricles, so that the posterior end (or apex) of the heart is 

 a blind end. Each ventricle gives off a single arterial 



