FORMATION OF CHYLE. 73 



known plastic substances, namely, albumen, fibrine, caseine. 

 It is maintained that the gastric juice is not of itself sufficient 

 for the conversion of these proteine bodies into nutritive matter, 

 and that the intestinal juice possesses, in a very high degree, 

 the property of preparing them for absorption. It appears to 

 be only in the upper part of the small intestine in which such 

 changes are effectually produced, or in that tract of the intes- 

 tinal canal where true villi exist. These several substances, 

 then, undergo such a change as permits them to be absorbed 

 by the intestinal villi, and, as it would appear, they are ab- 

 sorbed by the intestinal villi because they cannot pass through 

 the walls of the capillary blood-vessels of the intestinal mucous 

 membrane. 



Chyle. The fluid contained in the lacteals, during fasting, 

 is clear and transparent, differing in no respect from ordinary 

 lymph ; but while absorption is going on by the villi acting on 

 the chyme contained in the intestinal canal, that fluid becomes 

 milky, and acquires the other characters assigned to chyle. 

 The whiteness and opacity of the chyle appears to be depen- 

 dent on the presence of innumerable particles of oily or fatty 

 matter, of very minute size, and yet nearly uniform in that 

 respect, and said to measure nearly the 30,000th part of an inch 

 in diameter. These constitute what has been called the mo- 

 lecular base of the chyle. Their number, and by consequence 

 the opacity of the chyle, varies with the quantity of oily or 

 fatty matter contained in the food. The fatty nature of these 

 molecules is proved by their solubility in ether, after the eva- 

 poration of which various-sized drops of oil are deposited. It 

 has been remarked that these drops do not run together to 

 form large drops, as commonly happens to particles of oil. It 

 has hence been concluded that each molecule is coated over 

 with albumen, as happens when minute drops of oil are set free 

 in an albuminous solution. It is a confirmation of this sup- 



