512 ANATOMY OF VERTEBRATES. 



thoracic duct has been observed, with a similar arrangement, in 

 the Dog and Sea-otter. In most Carnivora the mesenteric 

 glands are aggregated in one mass, known to the old anatomists 

 as the ( pancreas Asellii : ' in the Weasel it is in two masses, and 

 in the Cat, Ichneumon, and Seal has been found more subdivided. 

 In these, however, there is one principal gland or * vasoganglion,' 

 the efferent vessels of which quickly unite into a trunk grooving 

 its dorsal surface in the Seal, from which two main canals proceed 

 to the thorax. In Ungulata and Quadrumana the mesenteric 

 glands are numerous. 1 have noticed a large one in the meso- 

 colon of the Echidna, near the rectum. The chyle-receptacle is 

 large and cavernous, sometimes bilocular, in the Horse : the 

 thoracic duct has shown varieties like those above described in 

 Man, but it always terminates in the precaval vein at the union 

 therewith of the two jugulars. In the Ox the lymphatic trunk 

 perforates the diaphragm by an aperture distinct from that of the 

 aorta : it usually bifurcates, sometimes becomes plexiform, in the 

 thorax : the two divisions diverging to the right and left inno- 

 minate veins formed by the junction of the jugulars and axillaries. 

 In the Hog the thoracic duct has been observed to terminate in 

 the azygos vein. The orifice of communication with the venous 

 system is usually defended by a pair of semilunar valves; but 

 varieties have been noted, and, after death, blood has been 

 observed in the thoracic duct of the Horse. 



Independent movements of contraction and dilatation have been 

 witnessed in the chyle-receptacle and lacteals of the Ox ; ! but no 

 rhythmically pulsating sacs have been detected in the absorbent 

 system of Mammalia, nor have other points of communication with 

 the venous system been uncontrovertibly determined, save those 

 above described. 



