576 TISSUE RESPIRATION 



and that beyond this limit all the oxygen taken up by 

 nervous substance is accumulated as an oxygen store. On 

 the other hand Winterstein showed in case of the isolated 

 frog's spinal cord that after asphyxiating his preparation 

 in an atmosphere of nitrogen there was no more oxygen 

 taken up at time of recovery than in ordinary respiration. 

 He concluded from this that oxygen storage does not take 

 place in the living bo<Jy, and that asphyxiation is not the 

 result of exhausting the oxygen store but is due rather to 

 accumulation of anaerobic cleavage-products apparently of 

 an acid character; of course lactic acid is to be thought 

 of at once. 



Gas Interchange of the Salivary Glands. The gas ex- 

 change of the salivary glands has been thoroughly inves- 

 tigated by Barcroft, at the suggestion of Langley (in se- 

 quence to the older studies of Chauveau and Kaufmann and 

 of Moussu and Tissot). Stimulation of the chorda undoubt- 

 edly increases the gas exchange of the submaxillary gland ; 

 the influence of sympathetic stimulation is more difficult to 

 determine, as the effect is masked by a reduction of the 

 blood flow. Barcroft believes, however, that the sympa- 

 thetic is not directly inhibitive to metabolism in the gland. 

 He showed (in collaboration with Piper) that injection of 

 adrenin calls forth a very much increased demand for 

 oxygen in the gland, apparently occasioned by stimulation 

 of the sympathetic. There first was a rise in blood pres- 

 sure after the injection, then an increase in the secretion 

 of saliva; the increase in oxygen consumption, however, 

 reached its maximum after the salivary secretion was almost 

 finished. The conclusion from this is that it is not the secre- 

 tion itself but the recovery and the restoration of secretory 

 material which calls out the main expenditure of energy. 48 



Gas Exchange in the Liver and Kidney. In case of 

 hepatic gas exchange it is apparently proved that it is more 



48 J. Barcroft, 1. c. p. 731-741; J. Barcroft and H. Piper, Jour, of Physiol., 

 44, 359, 1912. 



