ABSORPTION OF THE DIGESTIVE CAVITY. 



187 



FK;. 74. 



sorbents form a minute plexus beneath the mucous lining of the alimentary 

 canal along its whole extent; but in the small intestine they enter the villi, 

 at the extremities of which, indeed, they may be said to commence. Those 

 only arc entitled to the designation of " lacteals," which originate from the 

 intestinal canal below the point at which the biliary and pancreatic ducts 

 pour their contents into it; for above that point, the fatty constituents of 

 the alimentary matter are not in a state of sufficiently fine division to enter 

 them; and the absorbed fluid is consequently pellucid, instead of possessing 

 the milky aspect. Thus, then, we are to consider the lacteal portion of the 

 Absorbent system to be that part of it which is specially adapted, by its pro- 

 longation into the villi, for the reception of an Oleaginous fluid, which we 

 shall presently see to be taken up from the contents of the alimentary canal, 

 and to be prepared for entrance into the absorbents, by the epithelium-cells 

 at the radical extremities of those organs ( 134). 



134. The Villi are extensions of the mucous lining of the Intestinal canal, 

 which thickly beset its surface from the pyloric orifice to the csecum, that is, 

 through the entire length of the Small In- 

 testine, to which they are limited in Man. 

 They have usually somewhat the form of 

 the finger of a glove, being sometimes 

 nearly cylindrical, sometimes rather con- 

 ical, whilst they not unfrequently become 

 flattened and extended at the base, so that 

 two or more coalesce. Their length varies 

 from 4;th to \d of a line, or even more ; 

 and the broad flattened kinds are about 

 gth to -|-th of a line in breadth. In the 

 upper part of the small intestine, where 

 they are most numerous, it has been cal- 

 culated by Krause that there are not less 

 than from 50 to 90 in a square line; and 

 in the lower part, from 40 to 70 in the 

 same area. The details of their structure 

 are of extreme interest in reference to the 

 mechanism of absorption. If the plan 

 pursued by Teichmann, that of injection, 

 be adopted, the appearances presented are 

 those shown in Figs. 75 and 76, taken 

 from the beautiful plates which accom- 

 pany his work on the Lymphatic System. 1 

 From these it appears that the lacteals 

 commence either by a simple closed ex- 

 tremity, or by a loop, though in broad villi 

 a network is sometimes visible. The tube 

 or tubes occupying the centre of the villus 

 appear to possess perfectly definite walls, and are larger than the numerous 

 capillary bloodvessels which surround and are external to them. Their 

 average diameter is about -g-Joth or joVo^ f an * nc h > but they present 

 here and there slight dilatations and contractions, and at the base of the 

 villus terminate in a network of lacteal vessels immediately subjacent to 

 the Lieberkiihnian follicles (Fig. 76, b), termed by Teichmann, from the 

 closeness of the meshes, the Rete angustum. This plexus communicates 

 with another possessing larger vessels, which are supplied with valves, are 



Section of a Villus from the intestine of 

 a raljbit : above (a) is the central canal, 

 bounded on either side by the matrix (6), 

 which again is covered by long columnar 

 cells(c), containing a nucleus and granules. 

 The outer border of these cells is seen to be 

 striated. 



Ludwig Teichmann, Das Snugader System, Leipzig, 1861. 



