fi4 Dr. Marcet. Absorption of Oxygen and [June 4, 



Volume oxygen absorbed per minute 39'6 c.c. 



Volume oxygen absorbed per 100 air inspired 075 



Volume oxygen absorbed per 100 O inspired 3'61 



Weight oxygen consumed per hour 28'60 grams. 



Weight oxygen consumed per kilo, weight of body .... 0'416 



Weight CO 2 expired per minute 0'577 



The volume of air inspired was calculated from the nitrogen found 

 in the air expired, and this is one of the main features of the present 

 paper. A number of experiments were undertaken to try if any 

 accurate determination could be made of the air inspired and expired 

 by filling a counterpoise bell-jar with a measured volume of air, in- 

 spiring this air through the nose and expiring it into an empty 

 bell-jar through the mouth. The plan, however, did not prove suc- 

 cessful, and it was found impossible by this means to determine with 

 a sufficient degree of accuracy the differences of volumes between the 

 air inspired and expired. It then occurred to me that the volume of 

 nitrogen found in air expired might afford a means of determining 

 the volume of air inspired. According to one of the results obtained 

 from Regnault and Reiset's experiments there is, under ordinary cir- 

 cumstances, a trifling amount of nitrogen exhaled from the blood in 

 the process of respiration. The volume of this gas is, however, so 

 small that its mean proportion in dogs fed with meat was only found 

 to amount to the 0'0066 part of the oxygen consumed. This means 

 from 11 to 13 c.c. in 1800 or 2000 c.c. of oxygen consumed 

 and in about 33,000 c.c. of air breathed, a figure so low that, 

 practically, the nitrogen exhaled may be ignored in the calcula- 

 tion of the analyses. I have entered the correction in some of the 

 calculations, and it alters the volume of oxygen consumed by about 

 0'6 per cent., and that of the oxygen absorbed by 1 or 1'5 per cent. 

 These corrections are so small that I have not thought it worth while 

 to make them, and the nitrogen has been taken as the same in the air 

 expired and inspired. 



It was now easy to calculate the volume of air inspired. This 

 volume consisted of the atmospheric carbonic acid, oxygen, which 

 was taken in the proportion of 20'93 per cent., and nitrogen. The 

 atmospheric carbonic acid was determined in every experiment 

 by Pettenkofer's method ; it ranged from 5 to 10 parts in 10,000. In 

 the course of last April an additional ^window was made in my 

 laboratory, which allowed of improved ventilation. 



Having prepared a table of the constituents per cent, of the air 

 inspired, the volume of air inspired was calculated as follows : The 

 nitrogen (per ceiit.) in the air inspired is to 100, so is the nitrogen in 

 the air expired to the volume of air inspired. The volume of air in- 

 spired is thus obtained with much greater accuracy than by any 

 experimental method, as the nitrogen must invariably exhibit the 



