348 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in the central nervous system and in the testes of the rat without produc- 

 ing distortion of adjacent tissues. The addition of a low percentage of 

 urea to fixing fluids results in sharpening the chromosomes and preserving 

 the structure of the achromatic nuclear material. It may help the 

 penetration of fluids. Picro-formol-acetic solutions are more effective 

 when used at about 38° C. Cold is detrimental. Flemming's fluid is 

 more effective if used at 0° C, or even lower. Flemming's fluid is of 

 no value as a brain fixative at any temperature. At times (if urea is 

 added) it isolates metaphase and anaphase chromosomes in spermatocytes 

 somewhat better than any other fixative tried, except B 15, of which 

 the following is the formula : Picric acid, 75 c.cm.; formol, 25 c.cm. ; 

 acetic acid, 5 c.cm. : chromic acid, 1-5 grms. ; urea, 2 grms. Anilin 

 oil is an excellent substitute for the higher alcohol. Xylol shrinks 

 tissues more than the vegetable oils. 



Stains for Microscopical Purposes derived from Methylen-blue.* 

 L. Tribondeau and J. Dubreuil give the following procedure to obtain 

 the azur and the violet from methylen-blue : — To a 1 p.c. solution of 

 medicinal methylen-blue are added 5-10 p.c. of liquid ammonia. The 

 mixture is placed in a flask and heated in a water-bath to boiling. A 

 copious precipitate forms ; this is filtered off while hot. The filtrate, 

 placed in a large photographic dish, is evaporated in an incubator at 

 37°_40°. The residue consists of methylen-violet practically pure. 

 Some of the precipitate is gathered from the filter, but most is found 

 adhering to the wall of the flask. This is left, the flask not being 

 stoppered, in an ice-box for at least twenty-four hours. When the 

 precipitate has turned to a dark blue it is dissolved in distilled water. 

 It is then filtered and treated as the former filtrate. The powder so 

 obtained is the azur. The quantities of the azur and violet are about 

 equal. From these powders the authors make three staining solutions : 

 (1) An aqueous solution of azur ; (2) an aqueous solution of azur and 

 of violet, this they call polychrome blue ; {'6) an alcoholic-glycerinated 

 solution of azur and eosin, which they call azeo. (1) is a 1 p.c. solution 

 in distilled water ; (2) is a 1 p.c. solution of azur and violet, mixed in 

 the proportion of 1-3 by volume ; (3) is a mixture of azur and eosin ; 

 both are 1 p.c. solutions in alcohol and glycerin (75 ale, 25 glycerin). 

 Mixing them in about equal parts they are left for several days, and 

 then an excess of the alcohol-glycerin solution of azur is added, roughly 

 about 2 parts to 8. * 



Detecting Protozoal Cysts in Faeces by means of Wet-stained 

 Preparations.f — R. Donaldson's method consists in using a mixture of 

 equal parts of two stains used in any of the three following combin- 

 ations : — 1. 5 p.c. aqueous solution of Kl, saturated with iodine, to 

 which is added an equal volume of either — 2. (1) Saturated aqueous 

 solution of Rubin S ; or (2) saturated aqueous solution of eosin ; or (3) 

 Stephens' scarlet writing fluid. A few loopf uls of one of the above stain 



* Comptes Rendus, clxiv. (1917) pp. 551-3. 

 t Laucel), cxoii. (1917) pp. 571-3. 



