556 THE RESPIRATORY EXCHANGE 



flows from the submaxillary gland diiring stimulation of the 

 chorda tympani nerve contains a smaller percentage of water 

 than the arterial blood ; after the first minute of stimulation the 

 water lost from the blood exceeds in volume the saliva secreted. 

 The circulation of the blood through the gland during activity 

 is about six times as fast as during rest. Anaesthetics and leech- 

 extract alter the gaseous contents of the blood. All these factors 

 have to be taken into consideration. 



Experiments made by Barcroft and Brodie ( 29 ) have shown that 

 the production of a diuresis is accompanied by a marked increase 

 in the absorption of oxygen, but no change in the discharge of 

 carbon dioxide. Barcroft and Starling ( 30 ) have found that pan- 

 creatic secretion is accompanied by an increased absorption of 

 oxygen, and this takes place, although the rate of the flow of blood 

 through the organ may be sometimes greater and sometimes less 

 than in the condition of rest. There is no doubt that by similar 

 experiments much will be learnt about the respiratory exchange 

 of the different organs of the body. It is known that the gaseous 

 exchange is more active in some organs than in others, and even 

 in the same organ varies at different times according to the condi- 

 tion of activity. A study of the respiratory quotient has shown 

 that during hibernation oxygen may be absorbed without a corre- 

 sponding discharge of carbon dioxide ; during fattening the great 

 increase in the output of carbon dioxide is unaccompanied by an 

 equivalent absorption of oxygen ; in the former case there is a 

 great reduction in the muscular and glandular activity of the 

 body, in the latter the glandular activity is especially augmented. 

 The respiratory quotient of the normal animal must, therefore, 

 be considered as the resultant of the respiratory quotient of the 

 component organs, and it is probable that these differ in the 

 various organs, and even in the same organ during rest and activity. 

 It may be that some organs oxidise the waste products which are 

 carried to them by the blood which has passed through other 

 parts. Such a function Bohr and Henriques would ascribe to 

 the lungs, for they find that the absorption of oxygen and the 

 production of carbon dioxide by the lungs is about one -third the 

 total respiratory exchange of the body ; their results are, how- 

 ever, very variable, ranging from to 66 per cent., and as by 

 their method they failed to obtain the average rate of metabolism 

 during the whole experiment, their conclusions cannot be accepted. 



