TISSUES OF THE BODY. 



149 



Fig. 144. Cylinder cells of a 

 mucous membrane, arranged 

 perpendicularly (diagram- 

 matic), o, the cells; 6, the 

 intermediate matter; c, base- 

 ment layer; rf, the fibrous 

 tissue of the mucous mem- 

 brane. 



ance of an extremely delicate mosaic, similar to that of pavement epithe- 

 lium. But the fields are smaller, and the nuclei lie deeper than the edges 

 of the cell. 



Below, the pointed portions of the cell, separate ,at times from one 

 another (fig. 144), in which case the transparent intercellular-substance 

 becomes visible with considerable distinctness (&). 



But where the cells remain broad below, or serve to clothe strongly 

 curved surfaces (fig. 145), they lie in contact with one another throughout 

 their whole length. 



The nuclei of cylinder cells are roundish and 

 smooth, supplied also with nucleoli. The body 

 of the cell is seldom quite transparent, but usually 

 delicately granular and slightly clouded. The 

 membrane is generally very thin and fine laterally, 

 and is probably absent on certain portions of the 

 free base of the cell, or rather replaced by a soft 

 boundary layer ; at times, however, it is met with 

 apparently thickened by a transparent layer of 

 the cell-contents lying beneath it, containing no 

 ganules (fig. 143). 



Both as to size and form, our cells are subject to numerous variations. 

 Many appear tolerably short, while others are 

 long, and ab times also run out into long pro- 

 cesses below. Many of them again are broad, 

 so that the nucleus may be seen surrounded by 

 the membrane at no inconsiderable distance (fig. 

 143), whilst others remain much narrower. In 

 the latter case the envelope surrounds the 

 nucleus closely, or appears bulged out by the 

 latter. Finally, we meet with cells which con- 

 tain double nuclei. 



The relation of length to breadth in the cells 

 of the human small intestine, is as 0'0182- 

 0-0270 mm. to 0-0057-0-0090 mm. at its upper 

 end, while at the openings of the biliary and 

 pancreatic ducts the cells are narrower, with 

 the same length. Henle has seen unusually 

 slender ones in the human stomach. 



92. 



As has already been remarked in the general 

 section ( 50), cylinder-cells may display strange 

 deviations from the characters just mentioned, 

 especially those in the small intestine of man and 

 other mammals. 



The thickness of the border pierced with 

 minute pores (fig. 146 a, 147) is, in the rabbit, from 0'0017 to 0-0025 

 mm,, and the number of lines crossing it from 10 to 15. 



This secretion of the cell consists, as we have already mentioned, of a 

 coagulated protein substance, differing from the membrane, and offer- 

 ing but small resistance to the action of water, on the application of 

 which transparent drops rapidly well from it. Whether these pores 



Figr. 145. An intestinal villus 

 clothed with cylinder cells. 

 a, cylinder epithelium with 

 border; 6, vascular network; 

 c, longitudinal bundles of 

 muscular fibres; rf, chyle 

 vessel in the centre. 



