vui, D, 4 Wharton: Some Philippme Thalassemse 257 



various kinds are regularly scattered, becoming more compactly- 

 arranged toward the outer surface. In the upper part of the 

 oesophagus, from which the figure is taken, the muscle is moder- 

 ately thick, but it gradually becomes thinner and less compact 

 toward the posterior end. The endothelium consists of irreg- 

 ular, rounded cells which are very indefinite and indistinct, and 

 seem to lie in a matrix of some kind. The basement membrane 

 is distinct. 



The structure of the crop (fig. 7) differs considerably from 

 that of the oesophagus. The folds of the mucous membrane 

 increase so greatly that the surface seems to be covered with 

 villi. The epithelium is of the pseudo-stratified columnar type, 

 ciliated in the anterior part. The nuclei of the cells present 

 a very peculiar arrangement of the chromatin. In the newly 

 formed cells lying near the base of the epithelial layer, the 

 chromatin is in the form of many small discrete granules which 

 do not appear to be connected by any chromatin network. As 

 the cells approach the surface of the epithelium, the number of 

 these granules decreases. Finally, near the surface the nuclei 

 of some cells are clear and apparently altogether lacking in 

 chromatin. Small droplets of mucin appear in a fairly regular 

 row just below the inner surface of the epithelium. The main 

 part of the villi consists of connective tissue. In the outer part 

 of the submucous layer is a thin layer of circular muscles, and 

 on the outside of this, particularly toward the posterior end, 

 is a thin layer of longitudinal fibers. The endothelium is more 

 regular than that of the oesophagus. 



The walls of the midgut are much thinner than those of 

 either the oesophagus or crop. The projections of the mucous 

 membrane are in the form of low, parallel ridges running lon- 

 gitudinally, with a thin layer of epithelium and a very loose 

 connective-tissue layer. Here we have a definite sheet of lon- 

 gitudinal muscle fibers on the inside, but this has a thickness 

 of only 2 or 3 fibers, and outside of it is a thin layer of circular 

 muscles. In both the crop and the midgut the circular muscles 

 are scattered loosely in the connective tissue. 



The walls of the first part of the intestine are very thin, but 

 have much the same general structure as the midgut. The sub- 

 mucous layer is very loose, so that in some places there seem 

 to be sinuses. The collateral intestine has thicker walls, but 

 they seem to be of the same general arrangement as the main 

 part of the intestine. The second part of the intestine has the 

 siphonal groove running its entire length to the rectum. 



