STRUCTURE OF THE CORIUM. 223 



body. In consequence of the presence of these papillse on the 

 skin, the arrangement of the fibres undergoes some modifica- 

 tions. In particular, the fibres running parallel to the surface 

 penetrate the papillae, and are at the same time drawn out 

 into long loops. The course of these most superficial fibres is, 

 however, not quite straight, but gently sinuous, so that nei- 

 ther the surface of the corium nor that of the papillae is quite 

 plane. 



The vertical fibres of the corium also extend into the papillae, 

 accompanying the bloodvessels in their centre, and probably 

 terminating by free extremities. 



The surface of the corium is everywhere invested by a thin 

 membrane, that is most distinctly brought into view in speci- 

 mens prepared with chloride of gold. In these we find that 

 intermediate to the red or blue-coloured mucous layer and the 

 similarly coloured corium is a thin, transparent, and uncoloured 

 layer, in which, here and there, oval nuclei are imbedded, lying 

 parallel to the surface of the corium. The line of demarcation 

 between this membrane and the corium is not well defined, 

 but it is much more sharply expressed towards the mucous 

 layer, which, independently of slight furrows, is in many cases 

 finely toothed. Seen from the surface it exhibits fine ribs or 

 even prickles, which project amongst the cells of the mucous 

 layer. According to Czerny, after treatment with solution of 

 nitrate of silver, it presents a few areas like those seen in the 

 walls of the lymphatics. Elastic fibres constitute an essential 

 constituent of the corium, forming in the deeper parts a coarse- 

 meshed, but nearer the surface a closer plexus, and after the 

 clearing up of the connective tissue by means of acetic acid, 

 become conspicuous by their sharp outlines and spiral course. 



In addition to the elastic and connective-tissue fibres, cells are 

 found, which are either distributed as fusiform cells through 

 the fasciculi of connective tissue, or form stellate and anastomos- 

 ing cells, lying between the fasciculi in the deeper parts of the 

 corium, or between the individual fibres of the more superficial 

 parts. Fusiform cells also lie between the connective-tissue 

 fibres ensheathing the larger bloodvessels and capillaries. 

 Moreover we find round or oval cells, resembling the colourless 

 corpuscles of the blood in form and size, lying for the most part 



