CH. XXXVI.] 



ABSORPTION OF FATS 



547 



for fat absorption, and their name lacteals is derived from the milk- 

 like appearance of their contents (chyle) during the absorption of fat. 



The course which the 

 minute fat - globules take 

 may be studied by killing 

 animals at varying periods 

 after a meal of fat, and 

 making osmic acid micro- 

 scopic preparations of -the 

 villi. Figs. 366 and 367 

 illustrate the appearances 

 observed. 



The columnar epithelium 

 cells become first filled with 

 fatty globules of varying 

 size, which are generally 

 larger near the free border. 

 The globules pass down the 

 cells, the larger ones break- 

 ing up into smaller ones 

 during the journey; they 

 are then transferred to the 

 amosboid cells of the lym- 

 phoid tissue beneath : these 

 ultimately penetrate into 

 the central lacteal, where 

 they either disintegrate or 

 discharge their cargo into the lymph-stream. The globules are by this 

 time divided into immeasurably small ones, the molecular basis of chyle. 

 The chyle enters the blood-stream by 

 the thoracic duct, and after an abun- 

 dant fatty meal the blood-plasma is 

 quite milky; the fat droplets are so 

 small that they circulate without hind- 

 rance through the capillaries. The fat 

 in the blood after a meal is eventu- 

 ally stored up especially in the cells 

 of adipose tissue. It must, however, 

 be borne in mind that the fat of the 

 body is not exclusively derived from 

 the fat of the food, but it may origin- 

 ate from carbohydrate, and according 

 to some observers from protein also. 



The great difficulty in fat absorption was to explain how the fat 

 first gets into the columnar epithelium : these cells will not take up 



FIG. 366. Section of the villus of a rat killed during fat 

 absorption, cp, Epithelium; sir, striated border; 

 c, lymph-cells ; c', lymph-cells in the epithelium ; 

 I, central lacteal containing disintegrating lymph- 

 corpuscles. (E. A. Schiifer.) 



FIG. 367. Mucous membrane of frog's intes- 

 tine during fat absorption, ep, Epithe- 

 lium ; str, striated border; C, lymph 

 corpuscles ; I, lacteal. (E. A. Schiifer.) 



