1823.] an Examination of the Bloods 283 



follows that the quantity of particles appears to diminish in a 

 given quantity of blood. This was proved by the following 

 experiments : — A cat which had been previously bled for 

 another purpose, had venous blood again taken from it ; it con- 

 tained 862 parts of particles in 10000 of the blood ; when bled 

 the next day, the particles amounted to 856 parts. A strong 

 healthy cat was much bled from the carotid ; the blood con- 

 tained 1184 of particles in 10000 parts ; two minutes afterwards, 

 blood taken from the external jugular gave 1163 of particles; it was 

 then suffered to bleed five minutes, and blood then taken from 

 the jugular gave only 936 of particles. These two experiments, 

 the authors observe, leave no doubt as to the rapidity of the 

 absorption, and they indicate at the same time the plan to be 

 adopted for avoiding the error which it occasions. It appeared 

 probable that by slightly bleeding a strong animal, no sensible 

 effect would be produced ; a sheep being bled for this purpose, 

 from the carotid, 10000 parts gave 935 of particles, and venous 

 blood from the jugular gave 861 ; the blood of the dog and cat 

 present similar differences. Ten thousand parts of arterial blood 

 usually contain 100 parts more globules than venous blood. 

 Sometimes the serums are similar, sometimes slight uncertain 

 differences are perceptible. Care was taken in the experiments 

 related to obtain the venous before the arterial blood, in order 

 that the venous absorption, if it occurred, should not be in favour 

 of the circumstances related. 



In recapitulating the results of their labours, MM. Prevost and 

 Dumas remark. 



First, that arterial blood contains more particles than venous 

 blood ; 



Secondly, that the blood of birds is the most abundant in 

 particles ; 



Thirdly, that the mammiferae succeed birds in this respect, 

 and that it would appear that the blood of the carnivorous tribes 

 contains more particles than that of the herbivorse ; 



And, fourthly, that cold-blooded animals possess the smallest 

 number of particles. 



Finally, they observe, we acquire a direct proof of absorp- 

 tion by the veins after bleeding. We may even make use 

 of this principle for the purpose of explaining the anomaly 

 in the heron. It had lost much blood ; it had not taken any 

 food for some days ; and it seems fair to conclude from these 

 two circumstances, that the volume of particles having dimi- 

 nished, on the one hand, and not having been replaced, on the 

 other, necessarily remained below the mean. 



The apparent anomaly in the tortoise may be explained with 

 equal facihty. The life of this animal is almost suspended dur- 

 ing winter, so that many fewer particles of its blood are 

 destroyed. It must, however, lose water, partly in respiration ; 

 partly by transpiration; and partly by urine, the excretion of 

 which in abundance reguMiy continues. 



