CUTANEOUS AND MUCOUS FOLLICLES. 



559 



[Fig. 173. 



stomach. On the other hand, towards the pyloric extremity they have a much 

 more complex structure. Between the tubuli, blood-vessels pass up from the 

 sub-mucous tissue, and form a vascular network on its surface. From the 

 examination of these horizontal sections of the mucous membrane at various 

 depths, Dr. Todd* has ascertained that the tubuli are arranged in bundles or 

 groups, surrounded and bound together by a fine areolar membrane; the size 

 of the bundles, and the number of tubules contained in them, vary considera- 

 bly. The tubes do not, in general, open directly upon the surface, but into 

 the bottom of small depressions or pits, which may be seen to cover the mem- 

 brane. These pits are more or less circular in form, and are separated from 

 one another by partition-like elevations of the membrane, which vary in depth ; 

 and sometimes even by pointed processes, that have been mistaken by some 

 anatomists for villi. The diameter of these pits varies from about l-100th to 

 1 -250th of an inch; it is always greatest near the pylorus. When the sur- 

 face of the membrane, cleansed from mucus and epithelium-scales, is examined 

 with a sufficient magnifying power, it is seen that from three to five perfora- 

 tions exist in the bottom of each pit ; and these are the openings of the secret- 

 ing tubes. The Gastric fluid, elaborated by this Apparatus, having been 

 already made a subject of special consideration, ( 449, et seq.,) need not be 

 here described. 



705. The whole Mucous sur- 

 face of the Intestinal canal is fur- 

 nished with glandular follicles of 

 a very similar character; of which 

 some approach those of the sto- 

 mach in complexity of structure, 

 whilst others evidently corre- 

 spond with the crypts of ordinary 

 Mucous Membrane. An innu- 

 merable multitude of pores are 

 easily seen, by the aid of a simple 

 lens, to cover the whole internal 

 surface of the large Intestine; 

 and these are the entrances to 

 tubular follicles, closely resem- 

 bling those of the stomach, but 



more simple in structure. Their 



ccEcal extremities abut against the 



sub-mucous tissue: towards the 



end of the Rectum, however, they 



are much prolonged, and consti- 

 tute a peculiar layer between the 



mucous and muscular coats ; the 



tubes, which are there visible to 



the naked eye, being erect, pa- 

 rallel, and densely crowded. 



These glands probably form the 



peculiarly thick and tenacious 



mucus of the large intestine. In 



the small intestine, on the other 



hand, the coeca are less deep and 



their apertures are smaller. 



These apertures are, for the most 



A section of the Ileum, inverted so as to show the ap- 

 pearance and arrangement of the villi on an extended 

 surface, as well as the follicles of Lieberkiihn; the whole 

 seen under the -rhicroscope. A close examination of this 

 cut will show a great number of black points in the spaces 

 between the projections of villi : these are the follicles of 

 Lieberkiihn.] 



* Gulstonian Lectures on the Physiology of the Stomach, in Medical Gazette, 1839. 

 See also Dr. Sprott Boyd's Inaugural Dissertation on the Mucous Membrane of the Sto- 

 mach, in Edinb. Med. and Surg. Journal, vol. xlvi. 



