THE LYMPH AND THE CHYLE. 7 



We come now to consider the nature of the contents of the 

 thoracic duct. 



These, as already stated, vary according to the condition 

 of the animal ; thus, if it be fasting, the duct contains only 

 lymph ; if, however, the contents be examined soon after a 

 full meal, they will be found to present nearly all the characters, 

 physical and vital, of the chyle, and in addition, especially 

 in the fluid obtained from the upper part of the duct, a pink 

 hue, said to be deepened by exposure to the air. 



This red colour has been noticed by many observers, 

 and it is now generally agreed that it arises from the presence 

 in the fluid of the thoracic duct of numerous red blood 

 corpuscles. 



The question is not as to the existence of blood discs in 

 that fluid, but as to the manner in which their presence 

 therein should be accounted for, whether it is to be regarded 

 as primary and essential, or as secondary and accidental. 



Most observers agree in considering the presence of blood 

 discs in the chyle of the thoracic duct as accidental, although 

 they account for their existence in it in different ways. 



The distinguished Hewson * detected blood corpuscles in 

 the efferent lymphatics of the spleen, which empty their con- 

 tents into the thoracic duct, and in this way he conceived 

 that the fluid of that vessel acquired its colour. 



The accuracy of Hewson's observation, as to the lymphatics 

 of the spleen containing blood corpuscles, is confirmed by 

 Mr. Gulliver, of the fidelity, originality, and number of 

 whose remarks on the microscopic anatomy of the animal 

 fluids it is impossible to speak in terms of too high praise. 

 Mr. Gulliver detected blood corpuscles in the efferent lym- 

 phatics of the spleen of the ox and of the horse. 



Miiller, and MM. Gruby and Delafont, attribute the 

 presence of blood discs in the chyle to the regurgitation of 

 a small quantity of blood from the subclavian vein : if 

 they are really foreign to the chyle, this is the most probable 

 channel of their ingress. 



* Experimental Inquiries, part iii. Edited by Magnus Falkoner. 

 London, 1777, pp. 122. 112. 135. 



B 4 



