1 10 Chemical Researches on the Blood, 



have not hitherto been submitted to any accurate analysis, 

 on account of the difficulty of procuring them in sufficient 

 quantifies, and in a state of purity. Whilst engaged in 

 assisting Mr. Home in his physiological researches, several 

 opportunities occurred of collecting the contents of the 

 thoracic duct under various circumstances, and in different 

 animals; on other occasions Mr. Brodie has kindly fur- 

 nished me with the materials for experiment. 



SECTION II. 

 On the Composition of Chyle. 



The contents of the thoracic duct are subject to much 

 variation. About four hours after an animal has taken 

 food, provided digestion has not been interrupted, the fluid 

 in the duct may be regarded as pure chyle; it is seen en- 

 tering by the lacteals in considerable abundance, and is of 

 an uniform whiteness throughout. At longer periods after 

 a meal, the quantity of chvle begins to diminish, the ap- 

 pearance of the fluid in the duct is similar to that of milk 

 and water ; and lastly, where the animal has fasted for 

 twenty-four hours or longer, the thoracic duct contains a 

 transparent fluid which is pure lymph, 



A. The chyle has the following properties. 



1. When collected without any admixture of blood, it 

 is an opake fluid of a perfectly white colour, without smell, 

 and having a slightly salt taste, accompanied by a degree of 

 sweetness. 



2. The colour of litmus is not affected by it, nor that of 

 paper stained with turmeric, but it slowly changes the blue 

 colour of infusion of violets to green. 



3. Its specific gravity is somewhat greater than that of 

 water, but less than that of blood ; this, however, is pro- 

 bably liable to much variation. 



4. In about ten minutes after it is removed from the 

 duct, it assumes the appearance of a stiff jelly, which in 

 the course of twenty-four hours gradually separates into 

 two parts, producing a firm and contracted coagulum, sur- 

 rounded by a transparent colourless fluid. These spon- 

 taneous changes, which I have observed in every instance 

 where the chyle was examined at a proper period after 

 taking food, are very similar to the coagulation of the blood 

 and its subsequent separation into serum and crassamen- 

 lum ; they are also retarded and accelerated by similar 

 means. 



B. 1. The coagulated portion bears a nearer resemblance 

 to the caseous part of milk than to the fibrine of the blood. 



It 



