278 MANUAL OF HISTOLOGY. 



moses, this part of the corium lias been called the pars reticu- 

 laris corn, in contradistinction from the finer network formed 

 in the upper part, to which the name pars papillarls has been 

 applied. But neither between these two parts nor between the 

 subcutaneous layer and the corium is there any sharp dividing 

 line, the transition being a gradual one. 



As already mentioned, the size of the interfascicular spaces 

 depends upon the closeness of the anastomosis between the 

 bundles and fibres. The direction of the bundles corresponds 

 with that taken by the blood-vessels. 



The connective-tissue corpuscles of the corium resemble 

 those found in the subcutaneous layer, and also bear the same 

 relation to its connective-tissue bundles. From the upper 

 portion of the corium fibres pass upward to make the papillae. 

 The form of the papillae is very variable in different parts of 

 the body. Where they are most developed, as on the inner 

 surface of the terminal phalanges of the fingers and toes, they 

 are conical in shape. In some other regions they form only 

 slight elevations on the corium, giving a wave-like appearance 

 to its upper surface. They consist of a close network of white, 

 fibrous connective tissue combined, especially in the central 

 part of the papilla, with a large number of elastic fibres. Those 

 papillae which contain tactile corpuscles are called nerve-pa- 

 pillae. 



The corium is separated from the stratum mucosum by a 

 thin, transparent basement-membrane, containing oval nuclei. 

 Its under surface is not sharply defined, and from it prolonga- 

 tions pass upward between the cylindrical cells of the rete, 

 giving this surface a notched appearance similar to that ob- 

 served on the inner margin of the internal sheath of the hair- 

 follicle. 



Elastic fibres are present in large numbers in the corium, 

 especially in its upper part, where they form a network around 

 and between the white fibrous tissue-bundles. In the lower 

 part of the corium they form a large network, which becomes 

 finer as the surface is approached. The number of elastic 

 fibres increases with advancing years. With this increase of 

 elastic fibres there is a corresponding decrease of the white 

 fibrous connective-tissue cells (Ravogli). Numerous wander- 

 ing cells are met with in the corium, especially in the vicinity 

 of the blood-vessels and glands. Hair-follicles, sebaceous 



