346 THE HUMAN BODY. 



the portal vein to the liver; while those entering the lacteals 

 are carried into the left jugular vein by the thoracic duct. 

 As to which foodstuffs go one road and which the other, 

 there is still much doubt; sugars probably go by the portal 

 system, while the fats, mainly, if not entirely, go through 

 the lacteals. How the fats are absorbed is not clear, 

 since oils will not dialyze through membranes, such as that 

 lining the intestine, moistened with watery liquids. Most 

 of them, nevertheless, get into the lacteals as oils and not 

 as soluble soaps; for one finds these vessels, in a digesting 

 animal, filled with white milky chyle; while at other peri- 

 ods their contents are watery and colorless like the lymph 

 elsewhere in the Body. The little fat-drops of the emul- 

 sion formed in the intestine, go through the epithelial 

 cells and not between them, for during digestion these 

 cells are loaded with oil-droplets; as their free ends are 

 striated and probably devoid of any definite cell-wall, it 

 is possible that the intestinal movements squeeze oil- 

 drops into them. The cell then passes the fat to its 

 deeper end and, thence, out into the subjacent connective 

 tissue. Here " wandering cells" (p. 106) pick it up and 

 carry it into the central lacteal of a villus, where they 

 break up and set it free. In the villus there are all 

 the anatomical arrangements for a mechanism which shall 

 actively suck up substances into it. Each is more or less 

 elastic, and, moreover, its capillary network when filled 

 with blood will distend it. If its muscular coat (p. '321) 

 contracts and compresses it, causing its lacteals to empty 

 into vessels lying deeper in the intestinal wall, the villus 

 will actively expand again so soon as its muscles relax. 

 In so doing it could not fill its' lacteals from the deeper ves- 

 sels on account of the valves in the latter, and, accordingly, 

 would tend to draw into itself materials from the intestines; 

 much like a sponge re-expanding in water, after having been 

 squeezed dry. The liquid thus sucked up may draw oil- 

 drops with it, into the free ends of the cells and between 

 them; and by repetitions of the process it is possible that 

 considerable quantities of liquid- with suspended oil-drops. 



