350 



Dr. F. W. Pavy on the Physiology of [June 21, 



they show a want of proper precaution in collecting the blood, as well as 

 the effect of a fallacious method of analysis. It is necessary that both 

 the physiology and chemistry belonging to the course of procedure should 

 be free from sources of error ; and if the blood be collected directly after 

 the vessel has been cut down upon, it may be expected, as a result of the 

 effects of the operation upon the animal, to present a deviation from the 

 natural state, and more so especially after the exposure of the carotid artery, 

 on account of its deep situation and close contiguity to the pneumogastric 

 nerve. As I have stated, it is between the blood of the carotid artery 

 and jugular vein that the greatest disparity was noticed by Bernard, the 

 difference in one case amounting to *560 part per 1000, which is actually 

 a larger proportion of sugar than what I have found exists naturally in 

 the blood of the sheep and bullock. 



I will mention the course of procedure I have myself adopted to obtain 

 a true representation of arterial and venous blood in a natural state, and 

 give the results of the analysis of the samples. Experience has shown 

 that the effect of anaesthetics is to occasion a preternatural amount of 

 sugar in the blood. To strictly attain, therefore, the object in view it is 

 necessary that the collection of blood should not be made whilst the 

 animal is under their influence. 



In my first experiment I was under the necessity, on account of the 

 restrictions of the Vivisection Act, of collecting the blood instantly after 

 the destruction of life. Pithing was performed, and instantaneously 

 afterwards an incision was made across the jugular vein on the one hand 

 and the crural artery on the other. These vessels were selected from 

 their convenient situation for the expeditious performance of the opera- 

 tion in a manner to admit of the respective kinds of blood being obtained 

 in a pure or unmixed state. The following are the results of the analysis 

 of the counterpart samples of each. It will be seen that the amount of 

 sugar in the blood corresponds with what I have before represented as 

 naturally present, thus showing that no time was given between the 

 period of pithing and collection for the influence of post mortem change 

 in the liver to be exerted. 



Pour days ago the legal restriction I was before labouring under was 

 removed, and time has just been allowed previous to the termination of 

 the present session of the Eoyal Society for the performance of two ex- 

 periments, in which the blood was collected under natural conditions 

 during life. In these two experiments ether was administered to remove 

 sensibility during the exposure of the carotid artery and jugular vein. The 

 animals were then allowed to remain for an hour and a half to recover 



Sugar per 1000 parts. 



Crural artery. 

 [? } 795 (mean). 



Jugular vein. 

 5 1 -792 (mean). 



