CH. XXXIV.] 



ABSORPTION OF FATS. 



515 



small that they circulate without hindrance through the capillaries. 

 The fat in the blood after a meal is eventually stored up in the 

 connective-tissue 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 originate also both from 

 proteid and from carbohydrate. 



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

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

 up other particles, and it appears certain that the epithelial cells 

 do not in the higher animals protrude pseudopodia from their 

 borders (this, however, does occur in the endoderm of some of the 

 lower invertebrates) ; more- 

 over fat particles have never 

 been seen in the striated 

 border of the cells. 



Recent research has shown 

 that particles may be present 

 in the epithelium and lym- 

 phoid cells while no fat is 

 being absorbed. These par- 

 ticles are apparently proto- 

 plasmic in nature, as they stain 

 with reagents that stain proto- 

 plasmic granules ; they how- 

 ever also stain darkly with 

 osmic acid, and so are apt to 



be mistaken for fat. There is, however, no doubt that the particles 

 found during fat absorption are composed of fat. There is no 

 doubt that the epithelial cells have the power of forming fat out of 

 the fatty acids and glycerin into which fats have been broken up 

 in the intestine. Munk, who has performed a large number of 

 experiments on the subject, showed that the splitting of fats into 

 glycerine and fatty acids occurs to a much greater extent than 

 was formerly supposed ; these substances being soluble pass 

 readily into the epithelium cells ; and these cells perform the 

 synthetic act of building them into fat once more, the fat so 

 formed appearing in the form of small globules, surrounding or 

 becoming mixed with the protoplasmic granules that are ordinarily 

 present. Another remarkable fact which he made out is that 

 after feeding an animal on fatty acids the chyle contains fat. 

 The necessary glycerin must have been formed by proto- 

 plasmic activity during absorption. The more recent work of 

 Moore and llockwood lias shown that fat is absorbed entirely 

 as fatty acid or soap ; and that preliminary emulsification, 



L L 2 



Fig. <ji3. Mill-oils membrane of frog's intes- 

 tine during fat absorption, ep, epithe- 

 lium ; str, striated border ; C, lymph 

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



