202 Proceedings of Royal Society of Edinburgh. [sess. 
tion between defibrinated blood and dilute aqueous solutions of 
Hb0 2 . Thus — 
Sheep’s or ox’s blood in a corked bottle, even when not quite 
full, loses in about twenty-four hours its crimson hue, and becomes 
olaret coloured, while in a few hours more the spectroscope shows 
it to be HbO. This putrefaction-HbO is very easily re-oxidised 
into Hb0 2 , i.e., the pigment itself has not become decomposed, its 
-chemical integrity has not been compromised, although it has been 
reduced in and by decomposing blood. The pigment cannot be 
said to be decomposed so long as the HbO can become Hb0 2 
again. After 5 months, corked-up blood is alkaline, the pigment 
hsemochromogen, so that it must have passed through the stage 
of alkali-hsematin. 
The pigment in decomposing blood probably oscillates between 
these two states according to the amount of available oxygen pre- 
sent, for decomposing sheep’s blood 3 years old mixed with H 2 0 
in a hsematinometer (for it is too opaque when undiluted), showed 
the band of alkali-hsematin ; probably the hsemochromogen had 
been oxidised in the process. 
A dilute solution (*3 p.c.) of Hb0 2 in a test-tube loses its bright- 
ness on the fourth or fifth day, becoming slightly turbid, of a pale 
rusty-brown colour, slightly acid in reaction, and yields the 
spectrum of met-hsemoglobin ; at the end of 3 weeks it had 
become HbO, which, however, was easily oxidised to Hb0 2 on 
being shaken with air. Thus, while a dilute solution of the pig- 
ment of blood passes through an intermediate stage of met- 
hsemoglobin, the pigment in blood itself does not, but is reduced 
as its first change — a result evidently due to the development in 
-decomposing blood of some reducing materials which are absent 
from weak, watery solutions of the pigment alone. 
I found that thymol, as Yeo (8) had found phenol, delayed the 
appearance of these reducing decomposition-products in blood. 
XIV . — On certain other Pigments under Observation for 
Three Years. 
1. Reduced Hcemoglobin, made by Am 2 S, well corked, and not 
shaken with air, was still HbO at the end of five months. At the 
end of six months it was hsemochromogen, at the end of two years 
