240 SUMMARY OF CURRENT RESEARCHES RELATING TO 



examination, advises the following method. Round cover-slips thoroughly 

 cleaned are preserved ready for use in absolute alcohol. A mordant is 

 composed of 2 grm. of dry tannic acid, 5 grm. cold saturated solution 

 of sulphate of iron, 15 c.cm. of distilled water, 1 ccm. saturated alcoholic 

 solution of fuchsin, and to these he adds |-1 c.cm. of a 1 p.c. solution 

 of sodium hydroxyl ; the mixture after filtration being of a red-brown 

 colour, and to be used within 5 hours after its preparation. A stain of 

 carbol-fuchsin, prepared by adding to 1 grm. of granular fuchsin in a 

 flask 25 c.cm. of warm alcohol, shake, allow to stand for several hours, 

 and then dilute 4 or 5 times with a 5 p.c. solution of carbolic acid. 



A small loopf ul of previously boiled distilled water made cloudy with 

 the culture of the organism is placed on a cover-slip, which is held culture- 

 side upwards in forceps and passed through a Bunsen flame ; sufficient 

 mordant is then poured on it to cover the surface ; after |-1 minute 

 the mordant is washed away with tap water ; a small quantity of alcohol 

 is dropped on to the surface and again washed away ; then pour on the 

 stain and allow it to remain about £ a minute, then warm until it 

 steams ; when the slip is completely dry, treat with xylol and mount in 

 xylol-balsam. 



Demonstration of the Indol and Cholera-red Reactions.* — W. B. 



Wherry finds that nitrites and also probably nitrates gain entrance to 

 artificial media from various sources — certain waters, "peptones," and 

 filter papers ; and that a sufficient quantity of nitrites may be absorbed 

 from the air of the laboratory to yield a distinct indol reaction on the 

 addition of 0'5 c.cm. of chemically pure sulphuric acid. He therefore 

 recommends that media used in testing for indol or cholera-red re- 

 actions should be examined for nitrates and nitrites before use. The 

 author finds that the cholera spirillum does not produce nitrites in 

 nitrate- and nitrite-free " peptone " solutions. The cholera-red reaction 

 is not specific ; it must be distinguished from the purple-coloured indol 

 reaction. 



Method of Producing Chromatin Staining 1 in Sections.f — W. B. 

 Leishmann recommends the following method for staining chromatin in 

 sections. The sections (5//.) being fixed in the usual manner, are well 

 washed, after the final alcohol bath, with distilled water to remove all 

 traces of the alcohol, the excess of water being blotted away, and whilst 

 the section is still moist a drop of fresh blood serum is placed on it and 

 allowed to soak into it for 5 minutes ; the excess of serum is then blotted 

 ■away and the remainder is allowed to dry as a film on the section. 



A mixture of 2 parts of Leishmann-Romanowsky stain and 3 parts 

 of distilled water is poured on to the section and allowed to stain for 

 l-l£ hours, the stain being renewed from time to time, and is finally 

 washed off with distilled water. For purposes of decolorisation and 

 differentiation two solutions, freshly prepared with distilled water, are 

 used : (a) acid solution, 1 : 500 acetic acid, which removes excess of blue 

 and brightens the red tint of the chromatin ; (b) alkaline solution, 

 1 : 7000 caustic soda, which dissolves out the excess of eosin from the 



* Bureau Gov. Lab. Manila, No. 31, May 1905, p. 17. 

 t Journ. Hygiene, iv. (1904) p. 434>; 



