36 E. J. STIEGLITZ 



inasmuch as the experimental method necessitates the produc- 

 tion of a renal circulation nearly devoid of arterial blood and 

 therefore introduces the unfortunate factors of asphyxia and mal- 

 nutrition interfering with normal cellular activity. How essential 

 these two factors are, Martin Fischer (18) has demonstrated. 



A second type of investigation is that started by Heidenhain 

 (2, 3, 4, 19) on the route of colloidal dyes in their elimination 

 through the kidney. Gurwitch and many others have con- 

 tinued and elaborated such studies. Gurwitch (17, 20), work- 

 ing with 'indifferent' aniline dyes, agrees with Disse, v. d. Stricht, 

 V. Gehuchten, and Nicolas in having demonstrated the presence 

 of these dyes in the form of granules or masses contained in 

 vacuoles which migrate toward and burst on the surface. Sauer 

 (21), in opposition to such a conception, claims that the secre- 

 tion is diffuse in the cells and is never in an aggregated form in 

 cells or lumina of normal tissue. However, in such a discussion 

 it would seem that the reaction of the tissue at fixation is a 

 matter of considerable moment in determining the apparent 

 physical nature of the secretion. Sobieranski (10) lays stress 

 upon the inconclusiveness of their negative findings for the dye 

 in the glomerular capsules, saying that such negative evidence 

 is not proof, and offers three other explanations for such find- 

 ings: 1) That there the dye may be too dilute to be detected 

 microscopically ; 2) that the dye may be reduced and decolorized 

 at this point; 3) that the dye may pass through too rapidly to 

 be detected morphologically. Goldman (22, 23) and many 

 others, among them Evans (24), have devoted much investiga- 

 tion to the use of colloidal, so-called 'vital' and protoplasmic 

 dyes. But all these experiments deal with the elimination of a 

 foreign colloidal material which the kidney normally does not 

 eliminate and which in its physical properties differs considerably 

 from the normal urinary ingredients. 



Some very excellent work has been done, however, using elec- 

 trolytic salts instead of the dyes. Quincke (25) demonstrated 

 iron in the uriniferous tubules and their epithelium, but does 

 not localize this finding. Leschke (26) studied by microchem- 

 ical methods the excretion of sodium chloride, urea, phosphates, 

 uric acid, and other purines. He found that all these sub- 



