RESPIRATION. 519 



records a difference of 1.5 to 2. The figures by other observers vary from 

 0.5 to 1.5. The larger the volume of air respired, other things being equal, 

 the less the increase of temperature. 



The volume of expired air is from 10 to 12 per cent, greater than that of 

 inspired air, this increase being due to expansion caused by the increase of tem- 

 perature. When proper deductions are made for temperature and barometric 

 pressure, the actual or corrected volume is less by 2 to 2J per cent. 



Lessen estimated that 0.0204 gram of ammonia is eliminated per diem in 

 the expired air, but Voit's investigations indicate that expired air usually does 

 not contain even a trace of ammonia. 



Alterations in the Gases in the Blood. The blood in the pulmonary 

 artery is of the typical venous color that is, deep bluish-red. During its 

 passage through the lungs it becomes scarlet-red, or, commonly speaking, arte- 

 rialized or aerated. If we take arterial blood and deprive it of oxygen, the 

 color changes to a venous hue ; if now we shake the bluish-red blood in air or 

 O, the scarlet-red color is restored. We have here the suggestion that the blood 

 while passing the lungs absorbs O. Analyses show that not only does absorp- 

 tion of O occur, but that there is simultaneously with this an elimination from 

 the blood of CO 2 . 



Arterial and venous blood each contains approximately 60 per cent, volumes 

 of O and CO 2 ; that is, for about every 100 volumes of blood 60 volumes of gas 

 will be obtained. Such analyses demonstrate also that while the total volumes 

 per cent, of O and CO 2 are about the same, the proportions are different. The 

 following table, after Ellenberger, 1 gives the volumes per cent, of gases in the 

 arterial blood of various animals : 



Animal. Total. O. C0 2 . N. 



Dog 57.9 19.8 37.0 1.9 



Cat 43.2 13.1 28.8 1.3 



Sheep 57.6 10.7 45.1 1.8 



Rabbit 49.3 13.2 34.0 2.1 



Man 63.5 21.6 40.3 1.6 



Fowl 58.8 10.7 48.1 



Pfl tiger obtained as averages of analyses of arterial blood of dogs 58.3 

 volumes per cent., consisting of 22.2 volumes per cent, of O, 34.3 volumes 

 per cent, of CO 2 , and 1.8 volumes per cent, of N. Venous blood, according 

 to estimates by Zuntz based on a large number of analyses, contains 7.15 vol- 

 umes per cent, less of O and 8.2 volumes per cent, more of CO 2 . The quantity 

 of N is practically the same in both arterial and venous blood. 



The proportions of O and CO 2 in arterial blood vary but little in speci- 

 mens taken at random from the arterial system, while those of venous blood, 

 on the contrary, differ considerably according to the locality of the vessel as 

 well as to the degree of activity of the structures whence the blood comes. 

 Thus, venous blood from an active secreting gland differs very little in its 

 composition, gaseous and otherwise, from typical arterial blood, whereas when 

 1 Physiologie der Haussaugethiere, 1890, vol. i. p. 204. 



