56 DR DAVY ON THE COAGULATION OF THE BLOOD. 
moist fibrin, and both for a longer time and with more ammonia, but with re- 
sults so much alike, that I do not consider it necessary to detail them. They 
have all led me to the conclusion, that the volatile alkali, in its action on fibrin, 
is chiefly remarkable for rendering it viscid, and that its solvent power is 
inconsiderable.* My results do not perfectly accord with those obtained by Dr 
RicHarpson. In all the experiments he describes, quantities of lymph (10 grains) 
were dissolved, he states, completely in from fifteen to twenty-one days in mix- 
tures of water and ammonia, composed of 1000 grains of the former, and from 
5 to 2 grains of the latter, designated by ‘“‘ N H, 0,” a proportion this, even the 
largest, less than that I used. The difference I cannot account for. I thought 
it possible, that as fibrin freshly separated from the blood, and in its moist 
state, has a powerful attraction for oxygen, and in part liquifies with evolution 
of heat when exposed to its action,} that his experiments having been made, 
as I presume they were, without the exclusion of atmospheric air, the want 
of concord might thus be explained, but the last trial I have noticed does 
not support the conjecture. It is possible that the fibrin of birds may be less 
soluble than that of the mammalia, which he employed. But should it be so, 
the difference as to degree should not affect the argument. Even Dr Ricnarp- 
SON’s Own results, considering the proportions used of fibrin and ammonia, and 
the length of time required for the solution, seem to me in no wise to bear out 
the idea that the volatile alkali can be the solvent of fibrin in the blood in its 
healthy state. 
Dr RicHarpson, in support of his views, refers to some observations of the late 
Dr Brarr in proof of the existence of ammonia in the blood in disease. On con- 
sulting his writings, I find one instance recorded in which this alkali was detected 
in the blood of a person who had died of yellow fever, but in so small a propor- 
tion that none was “ yielded by heat alone, and not much on the addition of 
liquor potassee.” | In the majority of instances that he examined the blood from 
patients labouring under this disease, he found it, contrary to his expectations, 
normal, its corpuscles unaltered in form, and collected in rouleaux,—a circum- 
stance this, I cannot but think, incompatible with the presence of ammonia,—if 
its tendency is, as I have found, to render the blood viscid. My own experience, 
I may mention, as regards the state of the blood in yellow fever, accords with 
the ampler one of my valued friend. During life, I never found it otherwise than 
normal ; after death, in some cases, I found that “it gave off an ammoniacal 
odour when mixed with quicklime; whilst in others this odour was not per- 
* The fibrin, after solution, appears to be altered in its properties: obtained by evaporation (as 
the ammonia is expelled it forms as a pellicle) though still soluble in a slight degree in the volatile 
alkali, it is not rendered viscid, and, in consequence, there is no obstacle in the way of its filtration. 
+ See “ Researches Anatomical and Physiological,” vol. 11., p. 343. 
t “ Report on the First Eighteen Months of the Fourth Yellow Fever Epidemic of British 
Guiana,” p. 37. 
