VETERINARY PHYSIOLOGY 



amount of oxygen taken up. The proportion between the 

 C0 2 given off . 

 'taken up 1S called the Respiratory Quotient, and it is 



thus less than unity usually about '8 to -9 that is, for 

 every five volumes of oxygen taken up only four volumes are 

 given off in carbon dioxide, the remainder being combined 

 with hydrogen to form water. The various factors modifying 

 this quotient will be considered while dealing with the extent 

 of the respiratory changes (see p. 320). 



Expired air is saturated with watery vapour, and, therefore, 

 it usually contains more water than inspired air. 



Expired air also contains small amounts of organic matter, 



N 79 



o 21 



N 79 



O /6 



CO Z 



FIG. 143. Shows the Composi- 

 tion of Inspired and Expired 

 Air. 



FIG. 144. Shows the Difference 

 in the Gases of Arterial and 

 Venous Blood. 



which may give it an offensive odour. These may possibly be to 

 a small extent formed in the lungs, but they are to a greater 

 extent produced by putrefactive change in the mouth and 

 nose. It is probable that the accumulation of these products 

 in the air is one of the causes of the injurious effect of the 

 " foul air " in overcrowded spaces, but the evidence on this 

 point is inconclusive. 



Expired air is usually warmer than inspired air, because 

 usually the body is warmer than the surrounding atmosphere. 

 When, however, the temperature of the air is higher than 

 that of the body, the expired air is cooler than the inspired. 



This may be illustrated by the figures of an experiment 



Temperature of Inspired Air. Temperature of Expired Air. 



6-3 0. 30 C. 



17-19 C. 37 C. 



41 C. 38 C. 



44 C. 38-5 C. 



II. Effect of Respiration on the Blood. To understand these 

 changes in the air we must refer to the changes in the gases. 



