GBEAT LYMPHATIC VEIN. 



645 



with the thoracic duct by voluminous collateral branches, then unite with 

 it in such a way as to be inserted together by a single orifice above the gulf 

 of the jugulars."^ — Colin. 



Fig. 303. 



THE GREAT LYMPHATIC VEIN AND ENTRANCE OF THE THOKACIO DUCT. 

 A, Thoracic duct ; B, Great lymphatic vein, or right lymphatic trunk ; c, D, Anasto- 

 moses established between them near their insertion. 



DIFFERENTIAL CHARACTERS IN THE LYMPHATIC SYSTEM OF OTHER THAN SOLIPED ANIMALS. 



The lymphatic system, glauds and vessels, is more developed in Euminanta and the 

 Pig than in the Carnivora. 



In this respect the dcimestieated animals may be classified in the following order : 

 Ox, Sheep., Horse, Pig, Hog, Cat. 



EuMiNANTS. — " The tlioracio duct of large Ruminants, when it has entered the thorax 

 by a special opening In the diaphragm, almost distinct from that of the aortic arch, is 

 placed above and to the right of the aorta, between it and the spine. There, although 

 outside the corresponding intercostal arteries, it is completely concealed by a thick layer 

 of adipose tissue, in which are numerous subdorsal glands. Towards the fifth dorsal 

 vertebra, it receives a large lymphatic vessel coming from the enormous gland that exists 

 on the track of the oesophagus in tlie posterior mediastinum ; it then crosses the direc- 

 tion of the aorta and the oesophagus, passes to the left, gains the entrance to the thorax, 

 and opens in front of the first rib, above the junction of the left jugular with the anterior 

 vena cava.' 



" The varieties it presents in the Ox are numerous and very common. The rarest 

 disposition is that of a canal, single through- 

 out its entire length, such as it has been 

 described, and such as it is usually found 

 to be in small ruminants (Fig. 309). This 

 canal (Fig. 306), single at its origin and 

 for the greater part of its extent, often bifur- 

 cates towards the base of the heart, or at a 

 short distance from its insertion. Of these 

 t^vo branches, one passes to the right of the 

 oesophagus and trachea, the other to the left 

 of these, in foUowinj the ordinary direction ; 

 and, at the entrance to the thorax, they either 

 terminate separately, each in t!)e angle of 

 union of the jugular and corresponding axil- 

 lary vein, or together at the same point — the 

 gulf of the two jugular veins. ,,,,.„ ^ ■, i • • -i i vj- .j j 



" It happens that one of the branches of the bifurcated canal is m its turn subdivided 

 into two smaller branches, and that the other experiences at the same time a sunilar 



Fior 30.i. 



ENTRANCE OF THE THORACIC DUCT IN 

 THE OX. 



(1 Zundel has pointed out the curious fact, that in Euminants, the long, special, 

 lymphatic gland situated between the layers of the mediastinum and above the oesopha- 

 mis sometimes becomes so voluminous that its weight impedes rumination, especially 

 when the animal is lying. The bolus of food is prevented from ascending into the 

 oesophagus, and this may become a frequent and periodic cause of indigestion.) 

 44 



