302 CHYLE. [BOOK n. 



of the mesentery, transparent during fasting, and becoming milky 

 and opaque after a meal, especially after one containing much fat. 

 The contents of the thoracic duct therefore after a meal may be 

 taken as illustrative of the nature of the chyle present in the 

 lacteals, though strictly speaking the chyle of the thoracic duct 

 is mixed with lymph coming from the intestines and from the rest 

 of the body. During fasting the contents of the lacteals agree in 

 their general character with lymph obtained from other structures. 



The contents of the thoracic duct may be obtained by laying bare 

 the junction of the subclavian and jugular veins and introducing a 

 caiinula into the duct as it enters into the venous system at that point. 

 The operation is not unattended with difficulties. 



Chyle obtained from the thoracic duct, after a meal, is a white 

 milky-looking fluid, which after its escape coagulates, forming a 

 not very firm clot. The nature of the coagulation seems to be 

 exactly the same as that of blood. The surface of the clot after 

 exposure to air becomes pink, even though no blood be artificially 

 mixed with the chyle during the operation; the colour is due 

 to immature red corpuscles proper to the chyle. Examined micro- 

 scopically, the coagulated chyle consists of fibrin, a large number 

 of white corpuscles, a small number of developing red corpuscles, 

 an abundance of oil-globules of various sizes but all small, and 

 a quantity of fatty granules, too minute to be recognised under the 

 microscope as fatty in nature, forming the so-called ' molecular 

 basis.' Each oil-globule is invested with an albuminous envelope ; 

 this may be dissolved by the aid of alkalis, whereupon the globules 

 run together. The fibrin and white corpuscles are very scanty 

 (and the red corpuscles entirely absent) in lymph or chyle taken 

 from peripheral vessels; but they increase in quantity as the 

 lymph passes through the lymphatic glands. 



. The composition of chyle varies considerably not only in differ- 

 ent animals but in the same animal at different times. The average 

 percentage of solids may perhaps be put down as about 9, that of 

 proteid material as about 4 or 5, and that of fat as about 3 or 4 

 (though the latter may sometimes rise as high as 14), the remainder 

 being extractives and salts. The fats occur chiefly in the form of 

 neutral fats, though some soaps or fatty acids are present. Some 

 amount of lecithin, and cholesterin in considerable quantity, are 

 also frequently present. 



The proteids consist chiefly of serum-albumin, with a globulin, 

 probably paraglobulin, and a variable but small quantity of fibrin. 

 Among the extractives have been found sugar, urea, and leucin ; 

 since these are found in lymph as well as chyle they cannot be 

 regarded as derived exclusively from the intestinal contents. The 

 ash is remarkable for the abundance of sodium chloride and the 

 scantiness of phosphates. Iron is present in greater quantity than 

 can be accounted for by the presence of red corpuscles. 



