30 dr davy's miscellaneous observations on the blood. 



Now, after evaporation, crystals of muriate of ammonia, of a large size and in 

 abundance, were found on it. 



A fifth experiment, similar in manner to the last, with the exception that the 

 aqua ammonise (1 gr.) was spread as much as possible over the inside of the 

 phial, was made on the blood of a fowl (590 grs.) The blood coagulated in eight 

 minutes, and pretty firmly. Another portion, caught in a wine-glass, coagulated 

 in about a minute. Each was tested for ammonia, as in the preceding trial. 

 The blood in the wine-glass, after five minutes — the time that the acid was kept 

 over it — afforded no distinct trace of ammonia. The blood in the bottle, after 

 one minute, afforded ample proof of the evolution of ammonia in the large 

 crystals of the muriate which were formed on evaporation on the incumbent 

 glass. The contrast, indeed, was very striking, comparing the blood with and 

 without the addition of ammonia, as thus tested, and also by test-paper ; the 

 one, the former, having no effect during a minute that moistened test-paper was 

 held over it; the other, in the same time, producing a decided alkaline reaction. 

 On the following morning the crassamentum in the bottle was found slightly 

 contracted, though less than that in the wine-glass ; some reddish serum had 

 separated ; the blood corpuscles, whether suspended in the serum or retained in 

 the clot, were little if at all altered. 



From these experiments it would appear that the effect of aqua ammonia? 

 varies as to the quantity used, and this in a manner that could hardly be ex- 

 pected ; 31 per cent, occasioning a thick adhesive coagulum, with a change of 

 form of the red corpuscles, without the separation of any serum ; 25 per cent, 

 retarding the coagulation many minutes, but not preventing the separation of 

 serum and a certain contraction of the crassamentum ; 0*44 per cent, retarding 

 the coagulation and rendering the coagulum soft and viscid, barely semifluid, with 

 little separation of serum, and that viscid; lastly, 017 per cent, had little effect, 

 except that of retarding for a few minutes the coagulation, — the coagulum, when 

 formed, having very much its normal appearance. 



2. On the Fibrin of the Blood. — The fibrin used was obtained by washing the 

 clot which had formed in the first experiment. In its moist state it was slightly 

 viscid. By drying it lost 93 per cent. ; 25 grs. thus dried were put into a phial 

 with 273 grs. of aqua ammonias of sp. grav. -89, and secured by a glass stopper. 

 After eleven days it was not apparently diminished in volume : 41 grs. of the 

 clear fluid decanted and evaporated yielded only 1 gr. As the fluid became con- 

 centrated during the process, which was conducted at a low temperature, its 

 fluidity diminished, and when reduced to a drop it was still transparent. In its 

 dry state it appeared as a transparent film, and as seen under the microscope 

 with a high power it had a finely granular appearance. 



A second experiment was made on the same fibrin in its moist state, using in 

 place of aqua ammonise alone a dilute solution, consisting of 654 grs. of the alkali, 



