E. SMALL INTESTINE, BY E. VERSON. 571 



brane and the submucous tissue, Middeldorpf * and Briicke f 

 discovered a layer of organic muscular fibres, wliich can be 

 traced from one end of the intestinal canal to the other, and 

 from which processes are given off in various directions. 



In the muscular layer of the mucous membrane two laminae 

 of nearly equal thickness may be distinguished, named, in ac- 

 cordance with the prevailing direction of their constituent 

 fibres, the circular and the longitudinal fibre layer, though in 

 some places they run into one another. 



The muscular tunic frequently appears interrupted to permit 

 the passage of the lymph follicles, and also to receive the csecal 

 extremities of the Lieberkuhnian follicles ; or, lastly, it may 

 itself present a retiform arrangement, and it hence becomes in- 

 telligible how sections of the intestine sometimes exhibit con- 

 tinuous layers of circular and longitudinal fibres, sometimes 

 only one of these, and sometimes neither. 



We find, also, that in animals the prevalent arrangement ap- 

 proximates to one or other of these types, and I may mention 

 that in the child the circular layer is subordinate, so that the 

 direction of the fibres is almost entirely longitudinal, separating 

 in some places to form beautiful plexuses, whilst in the rabbit 

 the difference in the direction of the two layers is extremely 

 well marked, though they are very thin. 



We have already alluded to the processes given off by the 

 muscularis mucosae in speaking of the small fasciculi situated 

 between the acini of Brunner's glands. Those, however, which 

 pass towards the mucous membrane itself, and were discovered 

 by Briicke J and Kolliker, are of greater importance, and are 

 more constantly present. These form, on the one hand, long 

 bands, sometimes not exceeding a single fibre cell in thickness, 



* De Glandulis JBrunnerianis, Diss. Vratisl., 1846. 



f Ueber ein in der Darmschleimhaut aufgefundenes Muskelsystem, " On 

 a muscular system discovered in the Intestinal mucous membrane;" 

 Akademie der Wissenschaften in Wien, Februar heft, 1851. 



| Loc. cit. 



$ Ueber das Vorkommen von Glatten Muskelfastrn in Schleimhauten, 

 11 On the presence of smooth muscular fibres in mucous membranes ;" 

 Zeitschrift fur wissenschaftliche Zoologie, Heft 1, 1851. 



R R 



