THE INTESTINAL TUBULI AND JUICE. 



543 



and large intestines. They consist of multitudes of minute tubuli, 

 closed at their deep extremities, but opening on to the surface of the 

 mucous membrane, perpendicularly to which they are arranged, more 

 or less closely together. In the small intestine, they measure from 

 g^th to g^th of an inch in length, and about ^^th of an inch in 

 diameter. Their orifices are seen, Fig. 98, by aid of a lens, in all parts 

 of the small intestine, even on the valvulse conniventes, between the 

 villi, and also in little circlets, around the closed sacs of the so-called 

 agminated glands. Their total number has been estimated at several 

 millions. They are sometimes flask-shaped, but never subdivided, like 

 the gastric glands ; they are lined with a columnar epithelium, Fig. 

 99, and are surrounded by capillaries. 



They contain a transparent granular fluid, the intestinal juice 

 proper ; sometimes they are distended with opaque mucus, and des- 

 quamated epithelial ceils destitute of fat. The composition of the 

 intestinal juice is not well known ; it probably differs from ordinary 

 mucus, and has special properties ; it is colorless and viscid, and is 

 usually described as being strongly alkaline, but, according to others, 

 it is acid in a great part of the small intestine ; it contains from 2 to 

 3.5 per cent, of solid matter, in which is included an organic substance, 

 precipitable by alcohol and resoluble in water, but forming insoluble 

 precipitates with metallic salts. 



Attempts have been made to collect it, from animals, by ligaturing 

 previously emptied portions of intestine, or by forming artificial intes- 



Fig. 98. 



Fig. 99. 



Fig. 9S. Portion of the border of a Peyer's patch, magnified about twelve diameters. It shows the mi- 

 nute pointed processes named the villi of the small intestine, found both on the general surface, and also 

 on the lighter part or Peyer's patch. On this latter are seen the rounded or oval sacs, constituting the 

 agminated glands, with the villi between, not upon, them. Around the borders of these are circlets of the 

 orifices of the intestinal tubuli, or crypts of Lieberkiihn, others of which are seen, scattered over the gen- 

 eral surface between the villi. (After Boehm.) 



Fig. 99. Diagrammatic vertical section of one sac, and a part of another, from a patch of Peyer, with the 

 surrounding parts, g, the sac with its granular contents. /, one of the intestinal tubuli, crypts, or folli- 

 cles of Lieberkiihn, of which three others are seen, on the other side of the sac. , the intestinal villi, on 

 the surface of the mucous membrane, covering the patch, m, cut ends of the circular muscular fibres ; 

 beneath these, the longitudinal fibres, and the serous or peritoneal covering of the intestine. (After 

 Kolliker.) Magnified forty diameters. 



tinal fistulse ; but the fluid so obtained must differ from the normal 

 secretion. The quantity daily secreted in Man is uncertain, but is 

 doubtless considerable, especially after meals. 



The tubuli or crypts of Lieberkuhn of the large intestine, are 



