EPITHELIUM. 61 



Other varieties of epithelium will be taken up in connection 

 with the different organs. As already stated, many transi- 

 tional varieties occur, even in direct association with the typi- 

 cal forms we have described. 



Structure of epithelial corpuscles. According to the views 

 of Heitzmann, Klein, and others, the substance of the cor- 

 puscle is pervaded by a network, the minute fibres of which 

 may be seen under a lens of high power. The nucleus or cen- 

 tral body is also similarly provided. Within the meshes of 

 this network there is a hyaline substance, the abundance or 

 paucity of which determines the size of the meshes. 



The "granules," which have often been described, are, ac- 

 cording to this view, the nodal points of the mesh work. It 

 is also stated that the epithelial cells sometimes have a fine 

 limiting membrane (Klein) ; but even in such instances it IB 

 merely a condensation of the outer part of the corpuscle. 

 Within the nucleus there are also, according to the same ob- 

 servers, fibres, within the meshes of which are not infrequently 

 real granules (nucleoli). The epithelial corpuscles are at- 

 tached together, either by an interlacement of their processes, 

 as in the liver, or by a peculiar cement substance, as in pave- 

 ment epithelium, or by a continuity of their processes, as in the 

 rete mucosum. 



Recent histological studies have narrowed the field formerly 

 occupied by the epithelial bodies, and, in accordance with 

 these views, the flattened corpuscles which cover serous mem- 

 branes, such as the pleura and peritoneum, will be arranged 

 under the connective-tissue series, rather than under the epi- 

 thelial. The reasons for this change will be given in a subse- 

 quent chapter. 



BIBLIOGRAPHY. 



SCHULTZE, M. Die Stachel- und Riffzellen. Virchow's Arch., Vol. XXX., 1864, 



p. 260. 



SCHULTZE, F. E. Epithel. u. Driisenzellen. Arch. f. mikrosk. Anat. 1867. 

 RANVIER. Traite technique d'histologie. Paris, 1875. 

 DEL AFIELD. Studies in Pathological Anat. New York, 1878 et seq. 

 KLEIN and E. NOBLE SMITH. Atlas of Histology. 1879-80. 

 HEITZMANN. New York Medical Record, July 31, 1880, p. 133. 

 FREY. The Microscope and Microscopical Technology. New York, 1880. 



