CHAP. IX.J THE RETIFORM TISSUE OF THE INTESTINE. 401 



SECT. 2. THE RETIFORM OR RETICULAR (ADENOID) CONNECTIVE 

 TISSUE OF THE INTESTINAL Mucous MEMBRANE. 



The various structures which occupy the mucous membrane of 

 the intestine are imbedded in, and are supported by, a framework of 

 the particular variety of connective tissue which is known as retiform 

 or reticular tissue a tissue which serves a similar function in the 

 lymphatic glands and some other organs. " It is composed of a very 

 fine network or reticulum of connective-tissue fibres, which in their 

 behaviour to staining reagents and in their general microscopic 

 appearance closely resemble the white fibres of areolar tissue 1 ." 



It was, until lately, believed that the network of fibres of reticular tissue 

 are originally formed by the union of the processes of connective tissue 

 cells, and as a result of transformations of the protoplasm of these. This 

 view is probably incorrect. The fixed cells of the tissue, which were 

 supposed to be the centres from which the anastomosing fibres took their 

 origin, are now believed to be merely "applied to and wrapped round the 

 strands of the network, which may thus be in great measure concealed by 

 the cells. The tissue then appears formed of a network of branching and 

 anastomosing cells, and was for a long time so described, but if the cells 

 are brushed away or otherwise removed, as by a short treatment with 

 dilute alkali, the fibres of the reticulum come clearly into view. The true 

 structure of the tissue was first pointed out by Bizzozero 2 ." The fibres of 

 retiform connective tissue are probably in no sense developed from the 

 protoplasm of connective tissue cells, but are produced by changes occurring 

 in the original ground substance. 



" The view which supposes that a direct conversion of the protoplasm 

 of the connective tissue cells takes place into fibres, both white and elastic, 

 has of late years been widely adopted, but it seems to rest largely upon a 

 desire to interpret the fact in accordance with the conception (originally 

 formulated by Beale and M. Schultze), according to which every part of 

 an organised body consists either of protoplasm (formative matter), or of 

 material which has been protoplasm (formed material) ; the idea of a 

 deposition or change occurring outside the cells in the intercellular 

 substance being excluded. It is, however, not difficult to shew that a 

 formation of fibres may occur in the animal organism without a direct 

 transformation of protoplasm, although the materials for such formation 

 may be furnished by cells. Thus in those ccelenterates in which a low 

 form of connective tissue first makes its appearance this is distinguished 

 by a total absence of cellular elements, a ground-substance only being 

 developed and fibres becoming formed in it. Again, the fibres of the 

 shell-membrane of the bird's egg are certainly not formed by the direct 

 conversion of the protoplasm of the cells which line the oviduct, although 

 they are formed in matter secreted by those cells, and it is through their 

 agency that the deposit occurs in a fibrous form " (E. A. Schafer 3 ). 



1 E. A. Schafer, ' General Anatomy and Histology,' Part n. of Vol. 1 (see p. 239) of 

 Quain's Anatomy, London, Longmans, Green and Co., 1891. 



2 E. A. Schafer, op. cit. p. 240. 



3 E. A. Schafer, op. cit. p. 242. 



G. 26 



