1885.] 



Myolicematin and the Histohw matins. 



251 



always present, one between C and D, close to D, which corresponds 

 to the first band of the histohaematin spectrum, two very narrow and 

 sharp, of which the second is darker than the first between D and 

 E ; besides these there are one or two nearer violet, one covering 

 E and &, the other before F, which are not always present. The 2nd 

 and 3rd bands correspond closely to similar bands in the histo- 

 haematin spectrum, in which they may appear joined to form one 

 broad band. 



The colour of the pigment giving this spectrum is yellow or 

 reddish-yellow, but even in very pale muscles the bands can some- 

 times be seen, especially after tbe use of a reducing agent. 



Various attempts have been made to isolate myohaematin, but 

 owing to the coloured constituent being joined to a proteid, it will 

 not go into any of the usual solvents. It has been proved by pressing 

 out the plasma from frozen muscle that some of the myohaematin 

 belongs to the plasma, but even after this treatment, its bands are 

 seen better marked in the muscle than before. It has also been got 

 from blood-free muscle by digesting in pepsin solution, which, how- 

 ever, alters tbe pigment, as it no longer gives the original spectrum, 

 but another which is remarkable, as it is imitated closely by a spec- 

 trum sometimes seen in insect muscle without any treatment. 

 Obtained by this method, the pigment is of a yellow colour, and is 

 only soluble in water. 



Erom the changes which the histohaematins and myohaematin 

 undergo with oxidising and reducing agents, and for reasons given in 

 detail in the paper, I have come to the conclusion that these pigments 

 are concerned in the internal respiration of the tissues and organs in 

 which they are found. 



Spectrum of the Adrenals. — Another point of interest brought to 

 light by these observations is the occurrence of haemochromogen in 

 the medulla of the supra-renal glands of mammals ; thus in this 

 situation in man, dog, cat, ox, sheep, pig, guinea-pig, rabbit, and rat, 

 I have found haemochromogen, the bands of which are very dark; 

 and it would appear that this hasmochromogen is partially removed 

 by washing out the blood-vessels with salt solution. Hence, and 

 owing to the fact that elsewhere it is excretory, as in the bile, the 

 hasmochromogen of the adrenals appears to be excretory ; if so a 

 downward metamorphosis of haemoglobin, and probably (for reasons 

 given in the paper) of the histohaematins, is one of their functions. 

 Hence if by disease, or by artificial removal, this metabolism is 

 prevented, the incompletely metabolised pigments circulate in the 

 blood, and staining of skin and mucous membrane, as in Addison's 

 disease, may take place. In the urine of Addison's disease such an 

 imperfect metabolite occurs as I have already shown.* 

 # "Journal of Physiology," vol. vi, p. 37. 



