624 
DR. A. GAMGEE ON THE ACTION OF NITRITES ON BLOOD. 
tion of nitrite of amyl to a solution of haemoglobin, then treat the mixture with one- 
fourth of its volume of alcohol and expose it to cold, after some hours a brown deposit 
separates having very much the appearance of chocolate, and forming on microscopic 
examination the characters which have been already described as possessed by the bodies 
formed when haemoglobin is treated with other nitrites. These crystals can, like the 
others, be recrystallized without undergoing any change. On one occasion (20th Decem- 
ber 1867) I placed in a test-tube a magma of these crystals along with their mother- 
liquor, and on examining them now, after an interval of nearly three months, I find 
them still perfectly preserved and possessing all the characteristic features. This is 
probably due to the preservative influence of the nitrite, as I have hitherto failed in 
all attempts to preserve haemoglobin crystals. I may remark that when haemoglobin is 
dried, even in vacuo , the crystals always crumble to pieces. 
In order to show that the chocolate-coloured crystals of the nitrite compounds of 
haemoglobin are identical in form with those of O-haemoglobin, I shall place two micro- 
scopic photographs at the end of this paper 1 . The first represents the compound of 
nitrite of potassium with haemoglobin ; the second the body formed under the influence 
of nitrite of amyl, and which we may, reasoning by analogy, conclude to be a compound 
of nitrite of amyl with haemoglobin. These microscopic photographs I owe to the 
kindness and skill of Mr. Nicol, a very able photographer in Edinburgh. 
In now drawing the account of my experiments to a close, I shall state the conclusions 
which in my opinion may be legitimately drawn from them, and then add certain obser- 
vations on the relation of the nitrite compounds of haemoglobin to the 0-, CO-, and 
N 2 0 2 -compounds. 
Conclusions. 
1. When a solution of any nitrite acts upon the blood, peculiar changes occur in the 
colour, and simultaneously in the absorption-spectrum. 
2. These changes in the optical properties of blood are due to the formation of com- 
pounds presenting the same crystalline form, colour, and spectrum, whatever the nitrite 
which has been employed in their preparation. 
3. These bodies appear to be compounds of the nitrite used with oxidized haemoglobin. 
4. The substances formed by this process of chemical addition, although isomorphous 
with haemoglobin, differ from it in many of those remarkable properties upon which its 
functions in the economy of the body depend. By this process of addition the blood- 
colouring-matter appears to have lost its power of absorbing oxygen. 
5. The addition of nitrites to haemoglobin appears to result in the locking up of the 
loosely combined oxygen, so as to make it irremoveable by CO, or by a vacuum. 
Observations. 
We have hitherto been acquainted with haemoglobin itself as well as with its 0-, CO-, 
and N 2 0 2 -compounds. These compounds are all isomorphous, and possess almost the 
1 These have not been reproduced, but are preserved in the Archives of the Royal Society. 
