CUTANEOUS AND MUCOUS FOLLICLES. 



667 



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

 much more complex structure. Betweeen the tubuli, blood-vessels pass up 

 from the sub-mucous tissue, and form a vascular net-work 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 mem- 

 brane ; the size of the bundles, and the number of tubules contained in them, 

 vary considerably. 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 membrane. 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 l-250th of an inch; it is always greatest near 



[Fig. 271. 



Fig. 272. 



[Fig. 273. 



Portion of the mucous 

 membrane of the stomach, 

 showing entrances to the 

 secreting tubes, in pits 

 upon its surface. 





Vertical section of a stomach cell, with it 

 tubes : A in the middle region, B in the pyloric 

 region, a a. Orifices of the cells on the inner 

 surface of the stomach, b b. Different depths at 

 which the columnar epithelium is exchanged 

 for glandular, c. Pyloric tube, or prolonged 

 stomach cell. d. Pyloric tubes, terminating 

 variously, and lined to their extremities with 

 sub-columnar epithelium. 



From the dog, after twelve hours' fasting. 

 Magnified 200 diameters.] 



A. Inner surface of the stomach, showing 

 the cells after the mucus has been washed 

 out. Magnified 25 diameters. 



B. Columnar epithelium of the inner sur- 

 face and cells of the stomach : a. Free 

 ends of the epithelial particles, seen on 

 looking down upon the membrane, b. Nu- 

 clei visible at a deeper level, c. The free 

 ends seen obliquely, d. Deep or attached 

 ends of the same. The oval nuclei are seen 

 near the deeper ends. 



From the dog. Magnified 300 diameters.] 



* 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 Stomach, 

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



