158 



Dr. Harley on the Influence of Physical and [Mar. 10, 



the influence of chemical agents^ especially such as are usually regarded as 

 powerful poisons. 



The paper commences with a description of the apparatus employed, 

 and the method followed in conducting the inquiry ; and the details of the 

 several experiments are then given. The following is a brief statement of 

 the results. 



Part I. 



1. The experiments on diffusion showed that venous blood not only 

 yields a much greater amount of carbonic acid than arterial blood, but 

 also absorbs and combines with a larger proportion of oxygen. 



2. Motion of the blood was found to increase the chemical changes 

 arising from the mutual action of the blood and the respiratory gases. 



3. The results of the experiment on the influence of time led to the con- 

 clusion that the blood and air reciprocally act on each other in the same 

 way out of the body as they do within it, and that their action is not in- 

 stantaneous, but gradual. 



4. It was ascertained that a certain degree of heat was absolutely essential 

 to the chemical transformations and decompositions upon which the inter- 

 change of the respiratory gases depends. The higher the temperature up 

 to that of 38° C. (the animal heat), the more rapid and more effectual were 

 the respiratory changes ; whereas a temperature of 0° C. was found totally 

 to arrest them. 



5. The influence of age on the blood was found to be very marked, espe- 

 cially on its relation to oxygen. The older and the more putrid the blood 

 becomes, the greater is the amount of oxygen that disappears from the air ; 

 and although at the same time the exhalation of carbonic acid progressively 

 increases with the age of the blood, yet its proportion is exceedingly small 

 when compared with the large amount of oxygen absorbed. 



6. The average amount of urea in fresh sheep's blood was ascertained to 

 be 0'559 per cent., and its disappearance from the blood during the putre- 

 factive process was very gradual, there being as much as 0*387 per cent, in 

 blood after it was 304 hours old. 



Part II. 



The chemical agents employed were animal and vegetable products and 

 mineral substances. 



1. The effect of snake-poison was found to be an acceleration of the 

 transformations and decompositions occurring in blood, upon which the 

 absorption of oxygen and the exhalation of carbonic acid depend. 



2. The presence of an abnormal amount of uric acid in blood was also 

 found to hasten the chemical changes upon which the absorption of oxygen 

 and exhalation of carbonic acid depend. 



3. Animal sugar, contrary to what had been anticipated, retarded the 

 respiratory changes produced in atmospheric air by blood. 



