720 THE ANATOMICAL SEPARATION OF 



and unsatisfactory in many ways. For, unless Heidenhain's 

 directions are followed exactly, pigment may be seen also in the 

 cells of Bowman's capsule, especially if more than 5 c.c. of the 

 solution are injected. The use of indigo -carmine at all is open to 

 the serious objection that it readily undergoes reduction in the 

 living tissues into a colourless compound ; and this, coupled with 

 the diluteness of the glomerular nitrate, which would keep the 

 pigment in solution until it had undergone concentration in the 

 tubules, makes the microscopical appearances explicable also in 

 accordance with Ludwig's view. Carmine also is excreted by the 

 kidney, and has the advantage of undergoing no reduction in the 

 tissues ; but the injection of this dye by various observers has 

 led to contradictory results and equally equivocal microscopical 

 appearances. V. Sobieranski found the glomerular epithelium 

 stained, and granules of the dye in the cells of the convoluted 

 tubules. He pointed out that, as in the case of indigo- carmine, 

 the granules are always found in the portion of the cell bordering 

 upon the lumen of the tubule and never in the outer portion ; 

 he advanced this as evidence that the pigment is being absorbed 

 and not excreted by these cells. Other observers have pointed to 

 the same appearance as evidence of excretion ; and the granules 

 in secretory glands during activity do have this distribution. 

 Ribbert denied that carmine is to be found in the glomeruli, and 

 stated that the same result was obtained when laked blood, 

 which does pass out by the glomeruli, was injected at the same 

 time. On the other hand, Grlitzner found that, when a 2 per cent, 

 solution of gum was injected with indigo-carmine, the dye could 

 always be found in the glomeruli. 



The Anatomical Separation of the Glomeruli and Tubules. 

 Several attempts have been made to separate the activities of 

 these two structures by various operative procedures. Ribbert 

 made a bold attempt to separate the functions of the cortex and 

 medulla of the mammalian kidney by complete removal of its 

 medulla. He used rabbits for this purpose because they possess 

 but one pyramid. His method was to gouge away the whole 

 medulla of one kidney, leaving its cortex intact, and then to 

 remove completely the other kidney. The animals survived the 

 operation about two days, and secreted about twice as much of 

 a more dilute urine than the controls. He considered that his 

 experiments supported Ludwig's view. Boyd repeated these 



