THE PATHWAYS FOR LIPID ABSORPTION 121 



stuffs. The epithelium of the mucosa is made up of cylindrical cells which 

 measure 22-68 n by 6-9 p.. A homogeneous basal membrane lies under 

 it. On its free side, the surface is covered by cilia-like processes which were 

 formerly supposed to show ameboid movements related to absorption. 

 This concept has now been discarded. At present, the membrane is be- 

 lieved either to contain fine pores or to be composed of material having a 

 different chemical nature which is arranged in the form of pillars. In the 

 non-absorbing state, an alveolar region can be seen in the upper part of the 

 epithelial cells. Parallel fibrillar structures can also be noted which are the 

 so-called mitochondria of Benda (see Figure 6). It has been suggested 

 that changes occur in these mitochondria during absorption. 



The trophospongium or the Holmgren apparatus is another well defined 

 structure in the epithelial cell. 593-595 This is considered by Corti 596 to be 

 identical with the Golgi apparatus. 554 It is a glomerular structure lying 

 over the nucleus. Although several investigators were of the opinion that 

 this structure does not change during absorption, Mottram et al. b97 and 

 Cramer and Ludford 598 have reported that certain alterations do take place 

 coincident with absorption (see Figure 7). 



Leucocytes are present in great numbers between the cells and in the sub- 

 epithelial tissue. They can apparently pass through the mucosa to the 

 lumen of the intestine by ameboid movements, and are believed to be con- 

 cerned with fat absorption. It is also possible that the leucocytes pro- 

 vide a protective mechanism against the masses of bacteria in the lower 

 intestine, or against toxic substances produced by them. 



Lymphatic folliculi occur in the lamina propria of the intestinal wall, 

 where they are found as small solitary folliculi or as large Peyer's patches. 

 The lymphatic network, which is called the "Teichman net," surrounds 

 these patches, but does not enter them. The lymphatic vessels, which 

 provide a route for the transport of fat, begin in each villus, with one or 

 more round knotty swellings 554 ; under the villi, a second large plexus occurs, 

 as well as an additional one in the submucosal tissue. In the submucosal 

 plexus, there are valves which allow the lymph to flow only in one direction. 

 The small lymphatics from the villi eventually form larger vessels which 



593 F. Kopsch, Z. mikroskop. anal. Forsch., 5, 221-284 (1926). 



694 E. Holmgren, Anat. Anz., 20, 433-440 (1902); 21, 477-484 (1902). 



695 A. Guilliermond, Les constituants morphologiques du cytoplasme. HI. Le systeme 

 vacuolaire, ou vacuome, Hermann, Paris, 1934, pp. 63 ff. 



696 A. Corti, Richerche morf., 4, 313-422 (1924). 



697 J. C. Mottram, W. Cramer, ami A. H. Drew, Brit. J. Exptl. Pathol., 3, 179-181 

 (1922). 



* 98 W. Cramer and R. J. Ludford, J. Physiol., 00, 342-316 (1925). 



