THE EYE. 381 



or by salting with ammonium sulphate or magnesium sulphate. The 

 substance then appears as a violet amorphous material. On spec- 

 troscopic examination no specific bands are observed, but merely a 

 general absorption between D and C, which is especially marked 

 about E. 



Chromophanes. Chromophanes are pigments which apparently 

 belong to the lipochromes, and are found in the retinal cones of 

 reptiles and birds. They here occur in the form of red, green, and 

 yellow oil globules, which are quite distinct, and are situated at the 

 inner ends of the cones. The pigments in question are termed rhodo- 

 phane, chlorophane, and xanthophane, respectively. Unlike the 

 pigment of the rods, these chromophanes are apparently not affected 

 by light, unless exposed for several days. Of their significance, 

 nothing is known. 



The epithelial layer of the retina, which adjoins the choroid, con- 

 tains a black pigment, which is probably identical with that of the 

 choroid. This is termed fuscin, and belongs to the class of the mel- 

 anins, which comprise the black pigments that are found in the hair, 

 in the negro-skin, in melanotic tumors, etc. According to Lan- 

 dolt, this particular form contains C, 54.48 per cent. ; H, 5.36 ; 

 N, 12.65; O, 27.52. In addition iron is also found, and the 

 opinion has been expressed that the substance may be derived from 

 the coloring-matter of the blood. This supposition is strengthened 

 by the observation that the first appearance of the pigment in the 

 embryo coincides in point of time with the development of the 

 choroidal bloodvessels. 



Besides fuscin, a pigment of a yellow color has also been found 

 in the pigmented epithelial lining of the retina, which is termed 

 lipochrin. It is apparently a yellow lipochrome. 



The Choroid. Aside from the common components of connec- 

 tive tissue, the choroid, as has just been mentioned, contains a black 

 pigment, fuscin, which is probably identical with that found in the 

 pigmented epithelial lining of the retina (see above). 



THE EAR. 



The chemical composition of the organic portion of the middle 

 and the internal ear has not as yet been studied. The perilymph 

 and endolymph present an alkaline reaction, and, in addition to. the 

 common mineral salts of the lymph, contain traces of albumin, and 

 in some animals a mucinous body of unknown character. 



