COHNHEIM'S RESPIRATION APPARATUS 573 



measurement for one cubic centimetre of ox blood or cat's 

 blood, for which haemoglobinometric estimation had given an 

 average result of 0.197 ccm., was with this apparatus 0.198 ; 

 in one cubic centimetre of a soda solution of known content 

 determination yielded, instead of 0.421 cubic centimetres of 

 C0 2 , mean results of 0.420 and 0.423. These results indicate 

 an almost incredible exactness, and it is certainly not too 

 much to say that this method of Barcroft and Haldane 

 should be included among the most brillant achievements 

 thus far accomplished by precise work in the field of physio- 

 logical technic. 



In the study of tissue respiration occasionally there may 

 be occasion for analyzing the gases contained in salt solu- 

 tions. Thus, for instance, Vernon transfused excised mam- 

 malian kidney with Ringer's solution, and thereafter 

 analyzed the latter for its content of gas. The capillary tube 

 method of gas analysis employed in such studies, in which a 

 small bubble of gas that has been drawn into a capillary tube 

 is analyzed, has been brought to a high grade of efficiency 

 through the efforts of Barcroft and Hamill, Brodie and Cul- 

 lis, and of Krogh. 39 



Cohnheim's Respiration Apparatus for Isolated Organs. 

 Otto Cohnheim, moreover, has introduced a respiration ap- 

 paratus for isolated organs constructed on the principle of 

 the respiration apparatus of Atwater and Benedict. A given 

 amount of oxygen is circulated in a closed system ; due to the 

 oxygen consumption by the organ the volume of the oxygen is 

 lowered, and this diminution is determined by a manometer ; 

 and finally from a small bomb enough oxygen is allowed to 

 enter to bring the manometer back to its original register. 

 The loss in weight of the bomb gives the amount of oxygen 

 consumed; the carbonic acid is weighed after absorption 

 in moist soda lime. Many isolated organs may be studied 

 immersed in Ringer's solution; in other cases the oxygen 



89 Cf. T. G. Brodie, Jour, of Physiol., 39, 391, 1910. 



