ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 843 



epithelial nuclei to have taken a mnch deeper colour than the balance of 

 the structures. So marked was this in the experiments of the author, 

 that in perfectly fresh sections these were very sharply and neatly 

 differentiated. 



A very remarkable fact was brought out in the course of Pilliet's 

 experiments, viz. that when methyl-blue is introduced intra-peritoneally 

 into guinea-pigs, the glomerule is stained a rose-carmine. When 

 frogs were placed in an aqueous solution of methyl-blue, so weak 

 that they could live in it several days, it was found that while the 

 balance of the tissues were stained a diffused blue the glomerules showed 

 a colour varying from rose-carmine, or rose-red, to ochre-yellow, the 

 nuclei being more strongly tinted than the balance of the cell. In rats 

 in which the blue had been intraperitoneally introduced, the blue was 

 changed to red only on the surface of the glomerule. From these 

 experiments it follows that in certain cases the glomerule possesses a 

 peculiar oxidizing property in a high degree, since methyl-blue is a sub- 

 stance relatively refractory to oxidation. The significance of this 

 discovery is that, in the kidney, the capillary circulation of the 

 glomerules contains a large quantity of oxygenated blood, a fact which 

 demonstrates the organ to be a true reducing apparatus and not simply 

 a filter. We know that in the Eeptilia the dark-blood returning 

 from the tail is collected by a voluminous vein and carried to the 

 glomerulae, from which it departs, via the renal vein, not as black 

 but as red blood. The kidney in this becomes a true reducing appa- 

 ratus, partaking in this respect in the functions of the lung. The 

 experiment of Ehrlich in this direction, made some three years ago, 

 demonstrated these facts in a beautifully exact manner. By introducing 

 intravenously into the system two substances, the combination of which 

 gave rise to a coloured produce (indo-phenol), and which combination 

 could take place only where oxygen existed in exceedingly feeble 

 quantity, he arrived at a very exact knowledge of the degree of oxida- 

 tion existing in any organ or part. In a similar manner, conversely, by 

 using substances easily reducible (alizarine-blue, for instance), a scale 

 of oxygenation may be arrived at. He thus demonstrated the scale of 

 reductive power of the lungs, the cortical substance of the kidney, the 

 mucous membrane of the stomach, &c. Later he established the same 

 functions in the muscles, the liver, glands, &c. 



Staining-differences of Unstriped Muscle and Connective Tissue 

 Fibres.* — For distinguishing between smooth muscle-fibres and spindle- 

 shaped connective tissue-cells, M. E. Eotterer recommends the following 

 procedure. The fresh preparation is placed for 24 hours in a mixture 

 of 10 vols. 36° alcohol, and 1 vol. formic acid. The hardening fluid is 

 then quite extracted in water, after which the piece is treated with gum 

 and spirit and then sectioned. The sections are stained for 36 hours in 

 Grenacher's alum-carmine, and having been thoroughly washed, mounted 

 in glycerin or balsam. The protoplasm of the unstriped muscle-fibres 

 then appears red, the nucleus having a darker tinge. The cell contour 

 is quite sharp. Connective tissue is quite colourless or rose-coloured, 

 the cells are swollen, and their boundaries ill-defined. From this the 

 author concludes " that the contractile protoplasm of unstriped muscle 

 is not the same as that of connective tissue." 



* Comptes Eend. Soc. Biol., iv. (1887) p. 645. 



