RESULTS OF VITAL STAINING STUDIES 111 



RESULTS OF VITAL STAINING STUDIES 



Nothing remarkable was found in the vital staining studies. It 

 was at once plain that in spite of the poor penetration of the dye, the mito- 

 chondria of the convoluted apparatus by far outnumbered those of the 

 remaining tubular structure. Comparing controls to urea-fed rats of the 

 first group, there was no striking difference in the mitochondrial picture 

 in general. In all tissues studied the impression was gained that in the 

 control rats the mitochondria of the convoluted tubes were arranged in 

 distinct, closely packed stout rods or in bands of medium-size granules, 

 which extended about two-thirds into the cell and which were most nu- 

 merous near the base. In the collecting apparatus the finer, less numerous 

 granular mitochondria were distributed throughout the cell, leaving a 

 clear space around the nucleus. In the large tubules of Bellini the stout 

 rodlike form appeared again, but the number was few, and I judged that 

 more than half of the cells were mitochondria-free. In the urea-fed rats 

 the only difference in the mitochondrial picture was that the granular 

 form in general prevailed, but position and arrangement seemed to be the 

 same as in the controls. At any rate, no such morphological differences 

 existed as would warrant inferences as to differences in secretory activity 

 in the proximal convoluted tubules of the four groups of kidneys. 



The use of vital color reactions to solve the secretory problem of the 

 kidneys dates back to 1874, when Heidenhain ( 1 1 ) and Neisser first in- 

 jected dyestuffs into animals and found them in the convoluted tubules, 

 while the glomeruli and capsules were free from color materials. This 

 work in general has been substantiated by a number of investigators. 

 Since the exhaustive histochemical studies of Leschke(12), confirmed by 

 Oliver (13), it seems more clear than ever that urea and perhaps other 

 urinary solids are secreted (or excreted) in the convoluted apparatus, 

 while the glomerular apparatus is primarily concerned with the secretion 

 of practically solid- free fluids. The difficulty enters when one tries to 

 obtain evidence by vital dye studies as to whether the mitochondrial ap- 

 paratus is directly concerned with the secretory mechanism of the cell 

 of the convoluted tubule. One must not forget that most of the dyestuffs 

 used in histological methods are of colloidal nature, and consequently 

 when seen in cells that secrete substances crystalloid in nature they cannot 

 be used as an absolute criterion or parallel. The presence of dye mate- 

 rials in the renal cells brought there by the blood or lymph stream must 

 be considered a physical rather than a chemical reaction, as was brought 

 out by Suzuki (14) working in Aschoff's laboratories. He found that the 

 dye appeared in the urine long before the granular structures of the con- 

 voluted tubules, showed any signs of staining. Carmine in various- con- 

 centrations was used and at an "early stage of excretion" many finely 

 granular carmine casts were present in the collecting tubules. Suzuki 



