394 Royal Society : — 



exactly their true tints. The action of this reagent, however, takes 

 some little time at ordinary temperatures, though it is very rapid if 

 previously the solution be gently warmed. Hydrosulphate of am- 

 monia again produces the same change, though a small fraction of 

 the colouring matter is liable to undergo some different modification, 

 as is shown by the occurrence of a slender band in the red, variable 

 in its amount of development, which did not previously exist. In this 

 case, as with the tin salt, the action is somewhat slow, requiring a few 

 minutes unless it be assisted by gentle heat. Other reagents might 

 be mentioned, but these will suffice. 



8. We may infer from the facts above mentioned that the colour- 

 ing matter of blood, like indigo, is capable of existing in two states 

 of oxidation, distinguishable by a difference of colour and a funda- 

 mental difference in the action on the spectrum. It may be made to 

 pass from the more to the less oxidized state by the action of suitable 

 reducing agents, and recovers its oxygen by absorption from the air. 



As the term hcematine has been appropriated to a product of decom- 

 position, some other name must be given to the original colouring 

 matter. As it has not been named by Hoppe, I propose to call it 

 cruorine, as suggested to me by Dr. Sharpey ; and in its two states of 

 oxidation it may conveniently be named scarlet cruorine and purple 

 cruorine respectively, though the former is slightly purplish at a cer- 

 tain small thickness, and the latter is of a very red purple colour, 

 becoming red at a moderate increase of thickness. 



9. When the watery extract from blood- clots is left aside in a 

 corked bottle, or even in a tall narrow vessel open at the top, it pre- 

 sently changes in colour from a bright to a dark red, decidedly purple 

 in small thicknesses. This change is perceived even before the solu- 

 tion has begun to stink in the least perceptible degree. The tint 

 agrees with that of the purple cruorine obtained immediately by 

 reducing agents ; and if a little of the solution be sucked up from 

 the bottom into a quill-tube drawn to a capillary point, and the tube 

 be then placed behind a slit, so as to admit of analyzing the trans- 

 mitted light without exposing the fluid to the air, the spectrum will 

 be found to agree with that of purple cruorine. On shaking the 

 solution with air it immediately becomes bright red, and now pre- 

 sents the optical characters of scarlet cruorine. It thus appears 

 that scarlet cruorine is capable of being reduced by certain sub- 

 stances, derived from the blood, present in the solution, which must 

 themselves be oxidized at its expense. 



10. When the alkaline tartaric solution of protoxide of tin is 

 added in moderate quantity to a solution of scarlet cruorine, the 

 latter is presently reduced. If the solution is now shaken with air, 

 the cruorine is almost instantly oxidized, as is shown by the colour 

 of the solution and its spectrum by transmitted light. On standing 

 for a little time, a couple of minutes or so, the cruorine is again reduced, 

 and the solution may be made to go through these changes a great 

 number of times, though not of course indefinitely, as the tin must 

 at last become completely oxidized. It thus appears that purple 

 cruorine absorbs free oxygen with much greater avidity than the tin 



