394 Transactions of the Canadian Institute [vol. ix 



refer the localization of potassium more definitely to the individual 

 portions of the tubule. 



Similar condensations were found in the rabbit. But, comparing 

 the sections of the kidney from the pithed animal (Fig. 13, a, b), which 

 had been excised before the injection of the dextrose, with those from 

 the remaining kidney (Fig. 14, a, b) after it had been acted on by the 

 diuretic, a distinct difference would be seen between the two. In the 

 inner portion of the boundary zone from the former kidney there were 

 only about half as many tubules which exhibited the condensation about 

 the lumen as compared with those from the same region in the diuretic 

 kidney, a larger number of these latter also showing the potassium in 

 the lumen as well. These two kidneys gave the distinction between 

 active and inactive most clearly, the localization in the active kidney 

 being much more definite and uniform. 



The cat (Fig. 15) and pigeon (Fig. 16) also evidenced the peripheral 

 and central condensations. In some preparations from the kidney of a 

 foetal cat (Fig. 17) a few isolated convoluted tubules showed a certain 

 amount of peripheral condensation, but no central condensation was 

 observed. Sections from the kidney of Necturus were also prepared, 

 and in them was found a similar distribution, except that the cells seemed 

 to retain their individuality to a greater degree than in the kidneys from 

 the higher forms. This occasioned a distribution which tended to be 

 cellular rather than tubular in character. The same peculiarity was 

 observed in preparations of the pancreas from Necturus. 



The glomeruli in all the forms showed a characteristic pattern which 

 would be traced as lines composed of black dots of cobaltous sulphide 

 (Fig. 19). By comparison with stained and other preparations this 

 was judged to be largely in the walls of the blood vessels, with less marked 

 precipitations in the interepithelial walls and in the connective tissue. 

 In one preparation in which a surface view of Bowman's capsule (Fig. 20) 

 was seen the localization was confined to the cement substance of the 

 cells and to the connective tissue strands. Some of the potassium had 

 apparently slightly diffused before the reagent completely penetrated. 

 In the intertubular spaces the potassium was found concentrated on the 

 strands of connective tissue (Figs. 9 and 10). In a few preparations 

 from the dog's kidney the basement membrane became slightly separated 

 during preparation and was observed to be impregnated with the potas- 

 sium salt. In no instance was any potassium demonstrated in a cell 

 nucleus. 



That these concentrations of potassium were the result of actual 

 localization of the potassium salts in the kidney, and not artefacts, was 

 apparent from inspection of the sections. They could not have been so 



