600 
DR. A. GAMGEE ON THE ACTION OF NITRITES ON BLOOD. 
allowed to remain at rest for a considerable number of hours, so as to allow the froth to 
subside, and (unless this has been done immediately after the agitation of the tube had 
been completed) it is again clamped to the eudiometer. When the time has elapsed 
during which it is desired to keep the gas and blood in contact, the gas can be de- 
canted in the most perfect manner from the blood which remains in the laboratory-tube ; 
it is then measured and analyzed. The accuracy with which this separation of gas from 
the blood can be effected constitutes one of the greatest merits of the instrument for 
such experiments. Where gases are placed in contact with blood in ordinary absorp- 
tion-tubes, it is impossible to determine with sufficient accuracy the amount of gas 
remaining after the experiment. It is true that the gas may be decanted with a gas- 
pipette. It is, however, impossible in this way to decant the whole of the gas without 
carrying with it some of the fluid from which it is desired to separate it. The small 
gasometers of Bunsen 1 which were used by Dr. Harley 2 in his experiments on blood, 
although they allow of a transference of the gas which they contain to be easily effected, 
do not permit the gas which they contain to be sufficiently accurately read off to 
enable the exact change of volume which has occurred to be ascertained. 
An admirable manner of conducting these experiments consists in measuring out suc- 
cessively two, as nearly as possible equal, quantities of gas, which are transferred to two 
laboratory-tubes of the same size, each of which fits accurately to the eudiometer. Into 
one tube is introduced the normal blood, and into the other the same quantity of blood 
to which has been added the substance whose action it is desired to study. Both tubes 
are then agitated in the same manner and for a like time ; having been allowed to remain 
at rest for eighteen or twenty hours, one of the laboratory-tubes is connected to the 
eudiometer, and its gaseous contents are decanted and measured. This laboratory-tube 
having been emptied of blood and decanted, the' gas in the eudiometer is analyzed. The 
other laboratory-tube is then connected with the eudiometer, and the same series of 
operations gone through. If one sample of blood have been placed in contact with its 
measured volume of gas an hour later than the other, it will on the following day also 
be decanted, measured, and analyzed one hour later ; during the preceding hour there 
has then been ample time to analyze the gas from the first tube. 
I. One cubic inch of freshly defibrinated blood of the Sheep, which had been arterialized 
by shaking with air, was introduced in the laboratory-tube of Frankland’s apparatus. 
Then 2 cub. centims. of a solution of nitrite of sodium of unknown strength were intro- 
duced by means of a small pipettte. A quantity of air had previously been introduced 
into the eudiometer and measured; this was now passed into the laboratory-tube. 
The mixture of blood, nitrite, and air were then thoroughly agitated by shaking ; the 
blood readily acquired a chocolate-colour. After twenty-three hours the gas was de- 
canted from the blood, measured, and analyzed. 
1 Gasometry, translated by Dr. Roscoe, 1857, p. 20. 
2 “ On the Influence of Physical and Chemical Agents upon Blood,” Philosophical Transactions, 1865, 
p. 687. 
