CHEMICAL BASIS OF THE ANIMAL BODY. 271 



coloured red by acids and violet by alkalis. Since pyoxanthose 

 appears to be a product of the decomposition of pyocyanin, both 

 pigments may occur simultaneously in pus, in which case the fluid 

 is green. According to some more recent observations 1 pyocyanin as 

 judged of by its reactions with the chlorides of gold and platinum and 

 with other alkaloidal precipitants, as also from the formation of 

 crystalline compounds with acids, is closely related to the alkaloids. 

 Sweat is also occasionally coloured blue, in some cases by indigo- 

 blue (p. 201) as in urine, and it may be (?) by a pigment similar to 

 pyocyanin. 



Pigment of the suprarenal bodies. A suprarenal body when a section 

 is made through it is found to consist of an outer or cortical portion, 

 of a yellow colour, which constitutes the chief part of its structure and 

 an inner, medullary part of a darker colour. When the latter is acted 

 upon by ferric chloride it assumes a dark bluish- or greenish-black 

 colour, and if an aqueous extract of its substance (or the tissue itself) 

 be treated with an oxidising agent it turns red ( 498). It appears 

 therefore that the suprarenals contain some form of chromogen or 

 pigment-forerunner which gives rise under appropriate conditions to a 

 pigment. According to some observers extracts of the cortex show a 

 spectrum similar to that of the histohsematins (p. 235) while the 

 medulla gives one resembling hsemochromogen 2 . The pigment obtain- 

 able from the suprarenals has been investigated by Krukenberg 3 . By 

 a method for which the original paper must be consulted, he isolated a 

 brownish-red substance with an acid reaction, soluble in water and 

 alcohol, whose reactions were the same as those of extracts of the 

 suprarenals. None of the solutions showed any distinct absorption 

 bands. The whole subject requires further investigation, which might 

 be of interest in connection with the origin and causation of the 

 increased pigmentation of the skin observed when the suprarenals are 

 diseased. 



1 Gessard, Compt. Rend. T. xciv. (1882), p. 536. 



2 Mac Munn, Proc. Physiol. Soc. Dec. 1884 (Jl. of Physiol. Vol. v. p. xxiv). 



3 Virchow's Arch. Bd. ci. (1885), S. 542. 



