The call for oxygen by the tissues 



97 



opposite case may of course exist, that in which the freezing points 

 are the same, but in which nevertheless there must have been work 

 done because the molecular concentrations of the salts, though 

 jointly the same in each fluid, are severally different. 



Data of four experiments on the work of the kidney. 



Kidney secreting not at 

 all or to a trifling extent 



Kidney secreting 



0-04 c.c. 



0-03 c.c. 



0-05 c.c. 



0-04 c.c. 



0-09 c.c. 



0-09 c.c. 



2-1 c.c. 



2-8 c.c. 



Sulphates as ] 

 Urea = 0-28% 



NaCl = 0-39 L 



i = l"25 I 



i = 0-25/ 



Surgically, experiments of this character entailed a good deal of 

 difficult operating, which was carried out in the first two cases cited 

 above by Brodie, and if one followed the example of the surgical 

 text-books one would call it " Brodie's operation." These operations 

 were performed by him on dogs the second two experiments having 

 been upon cats. The operative procedure has not been materially 

 altered in the numerous operations which have since been per- 

 formed in the Cambridge Laboratory by Straub, Knowlton, Winfield, 

 Neumann and myself, on the kidneys and suprarenals of cats and 

 rabbits. The problem was to perform the necessary manipulations 

 upon the kidney without having the experiment upset by the surgical 

 shock involved in the exposure and manipulation of the intestines. 

 Its solution lay in the fact that the shock might be obviated by 

 getting rid of the intestines. The rectum was therefore tied in two 

 places and cut between the ligatures; the same was done to the 

 following structures, in order the inferior mesenteric artery, the 

 oesophagus, the coeliac axis, the superior mesenteric artery, and 

 the portal vein. Of course any minor vessels must also be ligatured ; 

 by this procedure the whole of the intestines, spleen, pancreas and 

 stomach may be removed, and with a little practice the blood pressure 

 at the end will be as high or higher than at the beginning of the 

 experiment. The animals were always anaesthetised, usually with 

 urethane. The blood from the kidneys was withdrawn through a 

 cannula placed in the vena cava, below the entrance of the renal 



B. R. F. 



