CHAPTER XIV. 167 



solution if you prefer it.) Or you may use a lower strength, viz. 

 0-1 per cent, at most (see Arch. mik. Anat., xxxvii, 1891, p. 249) ; 

 and this I find is generally preferable. 



Objects are supposed to have been well fixed twelve hours at 

 least in the strong chromo-aceto-osmic mixture, and stained for 

 some hours. In this way you get kinetic chromatin and nucleoli 

 alone stained. 



PODWYSSOZKI (Beitr. z. Path. Anat., i, 1886, p. 289) differentiates 

 (for from a few seconds to two minutes) in a strongly alcoholic 

 solution of picric acid, followed by pure alcohol. Same results 

 (except that the stain will be brownish instead of pure red). 



BABES recommends treatment with iodine, according to the 

 method of GRAM (see next section). This process has also been 

 recommended by PRENANT (Int. Monatsschr. Anat. } etc., iv, 1887, 

 p. 368). 



It has been shown by OHLMACHER (Journ. Amer. Med. Assoc., vol. xx, 

 No. 5, February 4th, 1893, p. Ill) that if tissues be treated with iodine 

 or picric acid after staining with safranin, there may be produced in the 

 tissue elements a precipitate of a dark red substance of a crystalline 

 nature, but of lanceolate, semilunar, falciform, or navicellar forms. 

 The precipitate is formed both in normal and pathological tissue, 

 readily in carcinomatous tissues ; and Ohlmacher concludes that many 

 of the bodies that have been described as " coccidia," " sporozoa," or 

 other " parasites " of carcinoma are nothing but particles of this 

 precipitate. 



See also the differentiation process of MARTINOTTI and RESEGOTTI 

 (Zeit. wiss. Mik., iv, 1887, p. 328) for alcohol-fixed material, and of . 

 GARBINI (Zeit. wiss. Mik., v, 2, 1888, p. 170). 



In preparations made with chromo-aceto-osmic acid, safranin 

 stains, besides nuclei, elastic fibres, the cell bodies of certain horny 

 epithelia, and the contents of certain gland-cells (mucin, under 

 certain imperfectly ascertained conditions). 

 The stain is perfectly permanent. 



287. Gentian Violet may be used in aqueous solution, or as directed 

 for safranin. 



In some cases it may be useful to employ the method devised by 

 GRAM for the differentiation of bacteria in tissues (Fortschr. d. 

 Medicin., ii, 1884, No. 6 ; British Med. Journ., September 6th, 1884, 

 p. 486 ; Journ. Roy. Mic. Soc. [N.S.], iv, 1884, p. 817). In this 

 the sections are treated, after staining, with a solution composed of 

 Iodine l g rm - 



Iodide of potassium . 2 grms. 



Water 300 



