MELANIN. 311 



strua, since as Jul. Vogel* was the first to observe, the tissues 

 may be infiltrated with sulphide of iron, from which, however, the 

 black pigment may very readily be distinguished by means of acids. 



Physiological Relations. 



Occurrence. This pigment exists as a thick investment on the 

 choroid coat of the eye. Whether it also occurs in other parts of 

 of the animal organism, is a point which cannot be decided, since 

 the other pigments of the same colour in morbid depositions either 

 have not been accurately analysed, or from their very small quan- 

 tity do not admit of analysis ; as for instance, the pigment of the 

 black bronchial glands, of the rete mucosum sen malpighianum of the 

 negro, of melanotic tumours, of the black serum which has been 

 occasionally observed, and of pulmonary tissue in certain cases. 



In the choroid coat the melanin is enclosed in peculiar hex- 

 agonal cells, but in the coats of the blood-vessels of frogs and 

 other amphibia it is found in jagged ramifying cells. In other 

 parts of the animal body in melanotic tumours for instance it 

 occurs, however, merely scattered among other cells or tissues. 

 Whether granular cells, when becoming obsolete, (such for example 

 as we find in old exudations,) contain actual melanin, is a question 

 which must still remain undecided. Sanguineous extravasations 

 are, however, not unfrequently converted into a mass, which is 

 coloured perfectly black by black pigment. 



Origin. The large quantity of iron contained in this pigment 

 indicates that it takes its origin from the hsematin. We cannot 

 recognise such a conversion by chemical means, till we are able to 

 demonstrate that pathological depositions of pigment contain true 

 melanin. Whatever view we may adopt regarding the production 

 of the black-coloured inflammatory globules, we must at all events 

 agree with Bruchf that they contain blood-pigment and the rudi- 

 ments of blood-corpuscles, even if we do not, like HasseJ, H. 

 Muller, and Pestalozzi, see true blood-corpuscles in these cells ; 

 if we examine the expectoration in a case of pneumonia in which 

 resolution is very gradually progressing, we find, on making a 

 perfectly unprejudiced observation, very many of these cells which 

 have the exact colour of blood -corpuscles. VirchowlJ has very 



* Pathol. Anat.S. 163 u. 311 [or English Translation, pp. 194 & 396.] 

 t Untersuch. zur Kenntniss des kornigen Pigments derWirbelthiere. Zurich, 

 1844. S. 42 ff, and Zeitschr. f. rat. Med. Bd. 4, S. 24 ff. 

 $ Zeitschr. f. rat. Med. Bd. 4, S. 1-15. 



Ueber Aneurismata spuria der kleinen Hirnarterien u. s. w. Wurzb. 1849. 

 II Arch. f. pathol. Anat. u. s. w. Bd. 1. 8. 401. 



