574 TISSUE RESPIRATION 



is introduced directly by way of the blood vessels of the 

 organ which may remain in situ** 



Thunberg's Microrespirometer. If, finally, there be 

 occasion to study the respiration of very small organs, 

 Thunberg's microrespirometer will serve the purpose fairly 

 well. The apparatus consists of two small flasks which are 

 joined hermetically by a horizontal capillary tube. A drop- 

 let of oil within this capillary tube moves toward the side of 

 lower pressure. An organ is placed in one of the flasks; 

 when if the respiration quotient 41 is greater than 1, that is 

 if more carbonic acid be produced than the amount of 

 oxygen consumed, the indicator drop moves away from the 

 organ, but in the reverse case toward the organ. If a small 

 amount of potassium hydrate, however, be placed at the 

 bottom of the vessel the carbonic acid is absorbed and the 

 movement of the droplet directly expresses the intake of 

 oxygen. 



By methods of this sort the individual organs have been 

 tested under the most varied physiological conditions. The 

 detailed results of study may be passed over and only the 

 most important points in question involved may be here 

 indicated with all brevity. The answers to these are at best 

 for the most part rather contradictory. 42 



Gas Interchange of Muscle. In case of the skeletal 

 muscles the relations between their functional efficiency and 

 gas exchange have been the subject of a large number of 

 investigations, particularly at the hands of C. Ludwig, 

 v. Frey, Chauveau and Kaufmann, Zuntz and Thunberg. 

 The last named author found by the aid of his microrespi- 

 rometer that the intake of oxygen by a frog's muscle is in a 

 general way a measure of the irritability of the muscle, but 



40 Otto Cohnheim, VIII internat. Physiol. Kongr. Vienna, Sept., 1910; 

 Zeitschr. f. physiol. Chem., 69, 89, 1910. 



41 The respiratory quotient, however, may be falsified in these experiments 

 by the fact that lactic acid of post mortem development displaces carbonic acid 

 from any carbonates which are present. 



^Literature: J. Barcroft, Ergebn. d. Physiol., 7, 699-762, 1908. 



