DR. A. GrAMGrEE ON THE ACTION OF NITRITES ON BLOOD. 
599 
own; and thirdly, has not so altered the compound of oxygen with blood-colouring- 
matter as to render the oxygen irremovable by carbonic oxide gas. 
A third method consists in adding the poisonous agent to blood, arterializing it as com- 
pletely as possible, and then boiling out the gases of the blood in vacuo , determining 
their amount and ascertaining their composition. 
It is well known that by merely exposing the blood to the temperature of the body in 
a Torricellian vacuum, the haemoglobin which it contains is reduced as completely as by 
contact with reducing-agents. The oxygen which has been in combination with it can 
therefore be determined with the greatest accuracy ; and in addition we can determine 
the amount and rate of evolution of the more or less loosely combined carbonic acid ex- 
isting in the blood. This method, taken by itself, possesses perhaps more value than 
either of the others to which I have alluded. 
The fourth method to which I must allude has already, in some cases, afforded informa- 
tion upon the action of certain poisons on blood which could scarcely have been observed 
in any other way, viz. spectrum analysis. If used in connexion with the three other me- 
thods of research which I have thought it proper to allude to in detail, we may expect 
that our knowledge of the mode of action of poisons on blood will become both accurate 
and complete. Having shown what light it appears to throw upon the action of nitrites 
upon blood, I shall detail the experiments which have been performed according to the 
three remaining methods. 
Experiments in which Blood acted upon by Nitrites was agitated with Air. 
All the gas-analyses made in the course of this investigation have been conducted with 
the admirable instrument of Dr. Frankland and Mr. Ward ; its value for such a re- 
search as the present one cannot be overestimated ; for, besides permitting of the most 
accurate analysis of the gases (which have been in contact with blood) being made, it 
enables the experimenter to separate perfectly the gas from the blood, and to deter- 
mine, with great ease and remarkable accuracy, the volume of the gas after contact with 
blood. 
The air or gas whose action upon blood has to be studied is first measured in the 
eudiometer, and then passed into the laboratory-tube; into the latter is then introduced, 
by means of a very perfect metallic syringe of the form shown in the annexed cut, an 
accurately measured quantity of the blood to be acted upon. The stopcocks of the 
eudiometer and laboratory-tube having been closed, the clamp which unites these is 
taken off ; the laboratory-tube is then closed with the thumb, and being taken out of 
the mercurial trough, is agitated as long and as violently as is required. It is then 
mdccclxviii. 4 N 
