DE DAVY'S MISCELLANEOUS OBSERVATIONS ON THE BLOOD. 25 



ceased to yield air, and this when the first trial was stopped before the exhaustion 

 of the air was nearly complete. This result, seemingly paradoxical, may have 

 been owing to ammonia formed, which may have fixed carbonic acid ; and that 

 ammonia was formed, was proved by the hydrochloric test and the production of 

 muriate of ammonia. It has been witnessed in the instance of both venous and 

 arterial blood, but most remarkably in the latter, and in warm weather oftener 

 than in cold. In support of the explanation offered, I may mention an experiment 

 on the blood of a calf, which had no food for about twenty hours before it was 

 killed. This blood, — it was arterial,— even at first gave off no air on careful 

 exhaustion. It was kept under an exhausted receiver from the 23d of April to 

 the 13th of May, during the whole of which time it gave off no air, though the 

 vacuum was as perfect as it could be made, and the pump was worked daily. At 

 the end of this time the serum had become dark red, and on examination the 

 blood was found in a state of incipient putrefaction and giving off ammonia. 



What struck me as most remarkable in these experiments with the air-pump, 

 was the comparatively small quantity of air, in most instances, disengaged from 

 the blood, and its total absence in others, taking into account the quantity of 

 carbonic acid liberated in the lungs during life in normal respiration, and also the 

 quantity of air, both oxygen and carbonic acid, found in the blood by the German 

 physiologists. Difference of temperature, comparing that of the hot blood cir- 

 culating in the lungs in birds as high as 106°-108°, and in the sheep, ox, and pig, 

 as high as 104°-106°,* with that of the blood of the same animals cooled to 50°- 

 55°, may partly account for the result first referred to, but the second adverted 

 to I cannot attempt to explain. 



Besides the foregoing trials with the air-pump, I have made some on the blood- 

 corpuscles, using very small quantities suspended in serum on a glass support. 

 The corpuscles were from the blood of the animals already mentioned, and also 

 of the frog and common trout. The results were all nearly similar : so long as the 

 corpuscles were floating in serum there was no appreciable change of form, but 

 if they were kept some hours under the exhausted receiver until they were left 

 apparently dry on the object-glass, then a change was perceptible in them. Under 

 the microscope they were found to have become greatly reduced in size, so as to 

 be seen with difficulty, and not without the nicest adjustment, and also altered 

 in form — the elliptical, as those of the bird, the fish, and batrachian, having 

 become rounded. These changes were very similar to those produced by the 

 action of water, and they may be accounted for, perhaps, on the idea that they 

 were owing to the hygroscopic quality of the corpuscles. I may further remark 

 that the effects on the corpuscles of the blood of the several animals tried some- 



* I have found the temperature of the blood of a pig, flowing in a full stream, 106°. The pig- 

 was in high condition ; the blood used was from it. 



