112 A CYTOLOGICAL STUDY OF THE KIDNEY CELL 



states that the presence of these granules does not point to carmine- 

 stained secretory granules derived from the epithelium of the convoluted 

 tubules, but rather to a product of precipitation of the dyestuff in solu- 

 tion, which is only in part passed through the convoluted tubules, while 

 some of it passes through the glomerular apparatus. He calls attention to 

 the fact that by pushing the carmine injections there is a gradual accumu- 

 lation of dyestuff in the renal epithelium which ultimately leads to stain- 

 ing of the true cell granules. The latter, therefore, must be sharply differ- 

 entiated from carmine granules. His results lead him to believe that the 

 carmine-absorbing granules have nothing to do with the actual secretion 

 of the dye material. 



The objection that might be raised is that carmine is not a specific 

 vital dye for mitochondria. Nevertheless the fundamental result remains 

 unchanged. Many investigators are in accord that the striations of the 

 convoluted tubules of the kidney are homogeneous rods when seen in 

 fresh tissues, but become granular in appearance under various condi- 

 tions. Some have considered this a true secretory phenomenon, others an 

 artefact. Arnold(15) thinks that the individual granules of the living 

 renal epithelium are pre-existing in the rods and joined together by seg- 

 ments. In my studies I have repeated Arnold's neutral red and methy- 

 lene blue method, and I am convinced that such a differentiation can be 

 obtained. The granules are stained red and the segments blue. There 

 are, however, certain objections. First of all, neither dye is specific for 

 mitochondria; secondly, in order to obtain a good differentiation of the 

 binding segments penetration has to be prolonged, and it is well known 

 that mitochondrial rods will break up slowly into granules if they are 

 exposed to changes in temperature or to substances poisonous to tissues. 

 This was shown by Lewis and Lewis (16) in tissue cultures, by Suzuki 

 in his carmine injections, and in various pathological conditions by 

 Ophiils(17), Takaki(18), Israel (19), Burmeister(20), Landsteiner(21), 

 Stork(22), Pfister(23), and others. 



While Janus green is considered a specific vital dye for mitochondria, 

 it is not a very satisfactory dye for the kidney as it penetrates very slowly, 

 even under the most favorable conditions, as on a warming stage. It has 

 the tendency to bring out a granular rather than a rodlike structure, and 

 the observation made here that the granular structure was seen more 

 often in the urea- fed rats may be the result of various circumstances. If 

 no warming stage is used the difference in temperature alone may be 

 sufficient to produce granular dissolution. If a stage is employed such 

 changes in osmosis as may be produced by evaporation may create granu- 

 lar changes. Cesa-Bianchi(24) has protested against the assumption of 

 pre-existing granules on the basis that .unstained fresh tissues have solid 

 rods. He maintains that the granular picture is created by fixation or by 



