ORGANS OF THE BODY. 499 



moans attain the same degree of development as those of the small intes- 

 tine, have been traced down into the rectum. 



The lymphatic apparatus, on the other hand, attains in the vermiform 

 appendix of man the most remarkable degree of perfection, as was first 

 shown by Teichmann. The external ramifications of the absorbent 

 vessels in the walls of the colon presents the same arrangement as in the 

 small intestines, and the same complicated distribution is evident as in 

 the muscular tunic of the latter. 



The nervous supply of the large intestine is derived from a wide- 

 meshed submucous plexus beset with ganglia. The plexus myentericus 

 presents the same peculiarities here as in the jejunum and ileum. 



No further reference need be made to the muscular and serous coats 

 of the large intestine. 



At the anus the columnar epithelium suddenly ceases, where the 

 epidermial cells commence, with a sharply defined line of separation. 



Close to the termination of the gut below, a certain admixture of 

 voluntary or striped muscle fibres presents itself among the unstriated 

 elements like what is seen in the oesophagus. 



The mode of development of the mucous membrane of the colon is the 

 same as that of the mucosa of the stomach (Koelliker). 



260. 



The physiological significance of the crypts of LieferkGhn, and tubular 

 glands of the large intestine, is still a point of considerable obscurity. 



They are, however, supposed to secrete what goes under the name of 

 the intestinal juice (succus entericus), a fluid in the production of which 

 the glands of Brunner, in the upper portion of the small intestine, must 

 also take a part. The secretion requires further examination before we 

 can pronounce upon its composition with any certainty. 



By a very ingenious mode of procedure, we have recently learned how 

 to obtain pure intestinal juice from the small intestine of dogs (Thiry). 

 This is then found to be a thin, strongly alkaline secretion of a light wine 

 colour, and sp. gr. of 1-0125. It possesses about 2'5 per cent, of solid 

 constituents, of which nearly 2 P 5 per cent, is albumen, and 0'3 per cent, 

 carbonate of sodium. It dissolves fibrin as long as alkaline, but neither 

 raw flesh nor boiled albumen are acted on by it. Moreover, it is said 

 neither to convert starch into grape sugar, nor to decompose the neutral 

 fats. This, however, is denied by Eichhorst, as regards the secretion of 

 the small intestine. The amount of this fluid poured out appears to be 

 very great. 



The secretion of the tubular glands of the large intestine has also an 

 alkaline reaction. The vermiform appendix is nothing but one large 

 absorbent apparatus. 



261. 



The pancreas, to which we now turn, exhibits, as regards its structure, 

 many points of similarity to the salivary glands. Its vesicles are roundish, 

 measuring 0'0564-0'0902 in diameter. The membrana propria is studded 

 over at certain points with nuclei, showing that here also, as in other 

 kinds of racemose glands, the construction, probably, out. of flat stellate 

 cells. 



The investing vascular network (tig. 496) is of the ordinary round form 

 of the whole of this group of organs. 



