110 Proceedings of the Royal Society 
as) of scarlet cruorine, were found to be extremely faint, and only 
visible when comparatively thick layers of fluid were examined ; 
whilst an additional and very faint absorption band in the red, 
occupying the same position as that of acid hmmatine, was seen. 
I at first thought that the acids, generated by the oxidation of the 
nitrite, had acted upon the blood-colouring matter in the same 
manner as weak acids usually do, effecting a partial conversion 
into heematin, so that whilst the bands of haemoglobin were yet 
visible, the one characteristic of haematin had been super-added. 
The total incorrectness of this view was proved on a more careful 
examination being made. On adding a few drops of ammonia 
to the blood-solution in which nitrite of amyl had effected the 
peculiar change alluded to, its colour again became red, and whilst 
the band in the red instantly and totally disappeared, the two 
absorption bands situated between D and E became much more 
distinct. Moreover, a third very faint absorption band was found 
occupying the junction of the orange and yellow, and just below 
Frauenhofer’s line D. On now treating the blood solutions with 
such deoxidising agents as protosalts of iron and tin and sulphide 
of ammonium, a spectrum, differing in no respect from that of 
reduced haemoglobin, w^as obtained, and the solution, when agitated 
with air, presented the most beautiful spectrum of oxy-hsemoglobin, 
i.e., the two bands a and /3 reassumed all the distinctness and 
beauty which they presented in the unaltered blood solution. 
Nitrite of ethyl was found to effect exactly the same alteration 
as nitrite of amyl, whilst, as might be expected, vinic and amylic 
alcohols, when added in small quantities to blood, were without 
any effect. When solutions of nitrite of sodium or of potassium 
were added to blood, instantly the same change was noticed as was 
produced by amylic and vinic nitrites. On very faintly acidulating 
blood with acetic acid, and subsequently adding a small quantity of 
a solution of nitrite of sodium, the same change occurred. 
In this case the change must have been due to the nascent 
nitrous acid, or to the nitric oxide secondarily resulting from it. 
In order to endeavour to determine whether the body produced 
under the influence of nitrites was really due to the action of 
nitrous acid, or whether, on the contrary, it was formed through 
the agency of nitric oxide, I performed the following experiment. 
Perfectly pure nitric oxide was passed into blood, exactly the same 
