CH. IV.] 



LYMPHOID TISSUE 



47 



and concealed by flattened connective-tissue corpuscles. When these 

 are dissolved by dilute potash, the fibres are plainly seen (fig. 71). 



The statement has been made that the fibres of retiform tissue are chemically 

 different from those of areolar tissue, in spite of the fact that they are indis- 

 tinguishable microscopically, and in many places continuous with each other. 

 Miss Tebb has conclusively proved that chemical differences do not exist between 

 the two groups of fibres ; both are made of collagen, and the substance termed 

 reticulin by Siegfried is an artifact ; it is merely collagen which has been rendered 

 istant and insoluble by the reagents >(alcohol, ether) used in its preparation. 



Adenoid or Lymphoid Tissue. 



This is retiform tissue in which the meshes of the network are 

 largely occupied by lymph corpuscles. These are in certain foci 



FIG. 72. 



72. Part of a section of a lymphatic gland, from which the corpuscles have been 

 for the most part removed, showing the supporting retiform tissue. (Klein and 

 Noble Smith.) 



actively multiplying ; they get into the lymph stream, which washes 

 them into the blood, where they become the colourless corpuscles. 

 It is found in the lymphatic glands, the thymus, the tonsils, in the 

 follicular glands of the tongue, in Peyer's patches, and in the solitary 

 glands of the intestines, in the Malpighian corpuscles of the spleen, 

 and under the epithelium of many mucous membranes. 



Basement Membranes. 



These are homogeneous in appearance, and are found between the 

 epithelium of a mucous membrane and the subjacent connective tissue. 

 They are generally formed of flattened connective-tissue corpuscles 



