DE. A. GAMGEE ON THE ACTION OE NITEITES ON BLOOD. 
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same physical characters; in all the O free haemoglobin has apparently linked itself 
to a molecule of O, CO, and N 2 0 2 respectively, the stability of the compound being 
least in the case of the O- and greatest in the case of the N 2 0 2 -compound. 
All these bodies, and preeminently the O-compound, appear to be examples of a class 
of bodies which stand, as it were, on the boundary line which separates chemical from 
physical combination — to be, in fact, examples of the class of so-called molecular com- 
pounds. Like other molecular compounds their composition varies greatly within certain 
limits, and is influenced by circumstances and conditions which have no action on che- 
mical compounds proper 1 . 
That a body possessing such a very complicated molecular structure as haemoglobin 
should present numerous points of attachment, as it were, for the linking-on of such 
active, condensed bodies as the nitrites, is more than probable, and it is not remarkable 
that, as in the case of other combinations of a molecular kind, such as the union of salts 
with their water of crystallization, of bases with sugar, of albumen with metallic oxides, 
of iodine with the compound ammonias, the amount of the simpler body added to the 
more complex, should vary within wide limits. 
Simultaneonsly with the observations which I have conducted, and which have shown 
the power of nitrites to combine with haemoglobin, those which have lately been made 
by Hoppe-Seyler and Preyer, although discrepant in many particulars, seem to agree 
in proving that hydrocyanic acid possesses the property of linking itself to haemoglobin, 
forming a body which is isomorphous with it, but which physiologically is an inert 
body, having lost the power which, normally, haemoglobin seems to possess of ozonizing 
atmospheric oxygen. 
1 My friend Mr. James Dewar, Assistant to the Professor of Chemistry in the University of Edinburgh, first 
suggested to me the idea of the molecular nature of the compounds of haemoglobin. 
