PIGMENTATION. 61 



their subsequent metamorphoses in the interior of this capsule, they lose 

 their circular outline, grow darker, and finally run together to form a 

 dark-brown or black pigmentary deposit. 



§ 58. After the colouring-matter has escaped from the blood- 

 corpuscles, and has permeated the surrounding tissues, we notice 

 that their elements vary in their capacity for taking up the pig- 

 ment which is thus presented to them. T\^e remark preferences 

 quite as decided as those which are manifested during the soaking 

 of dead tissues in an ammoniacal solution of carmine. The cells 

 attract the pigment more powerfully than the intercellular sub- 

 stances, homogeneous membranes, elastic fibres, &c. The cells 

 therefore appear, even at this stage of the process, to be most 

 intensely stained of a yellow or brown colour. But the colora- 

 tion with hcematin differs from staining with carmine, in that the 

 nucleus does not exhibit a greater attraction for the pigment than 

 the remaining portion of the cell. On the contrary, the nuclei 

 are remarkable for taking no part in the change, appearing at a 

 later period as colourless discs in the interior of the tinted proto- 

 plasm. 



The stage of diffuse imbibition is followed by the precipitation 

 of the pigment in a granular or crystalline form. This, too, we 

 had occasion to observe during mortification. Hence, as also 



Fig. 22. 



Cells in various stages of pigmentary infiltration ; («, h, c, e), 

 from a melanotic cancer; d, Pigmented epithelium from 

 the vessels (same specimen), ■^^. 



because it occurs not only in the tissue-elements themselves, but 

 in the free fluid hetiveen them as well, we are justified in viewing 

 it as a purely chemical phenomenon, having no connexion with 

 the vital properties of the part. True that the crystalline deposits 

 (hsematoidin), which are least likely to depend on the action of 

 the cells, are more frequent in the free fluid than in the interior 

 of the cells ; still, coloured crystals have also been detected in 



