132 PHYSIOLOGY AT THE FARM. 



tery, and enter the numerous mesenteric glands placed between 

 that fold of the peritoneum. 



Mesenteric Glands. The mesenteric glands are numerous 

 probably not much less in number than two hundred 

 their medium size, that of an almond. They are much more 

 numerous in that part of the mesentery which supports the 

 jejunum. They are, in general, at least two inches distant 

 from the border of the intestine. When the lacteal vessels 

 have passed through one or other of these glands, they, by 

 degrees, unite as they near the attached part of the mesen- 

 tery that is to say, two or three join into one larger vessel. 

 Thus they become fewer and fewer in number, until, finally, 

 near the root of the anterior mesenteric artery, they have 

 become reduced to two or three trunks, which end in the 

 thoracic duct. At other times a considerably greater number 

 of trunks open, one by one, into that duct. Such is the 

 course of the lacteal s coming from the whole of the small 

 intestine, and from the transverse colon. Those from the 

 inferior parts of the colon join some of the lumbar lymphatics, 

 or turn forwards, and, by a distinct trunk, end in the posterior 

 part of the thoracic duct. To the posterior extremity of the 

 thoracic duct also proceed, from behind forwards, the lymphatic 

 vessels from the lower limbs, so that it is correct to say that 

 the thoracic duct begins at the common union of these lym- 

 phatics with the trunks of the lacteal system ; and here there 

 is a dilatation which more truly deserves the name of " recep- 

 taculum chyli " than in the human structure. 



Thoracic Duct, The thoracic duct extends from the loins 

 to the neck. At first it lies to the right side, or above the 

 aorta, passes in contact with the right crus of the diaphragm, 

 and gets into the thorax, where it is seen on the inferior sur- 

 face of the bodies of the dorsal vertebras, between the aorta 

 and azogous vein the last being to its right side. By degrees 



