112 THE AMERICAN MONTHLY [April, 



MICROSCOPICAL MANIPULATION. 



Preparing and Staining Yeast. — Dr. H. Moeller used for 

 fixing yeast preparations a i per cent, solution of iodide of potas- 

 sium saturated with iodine, this fluid ten times diluted, and also 

 iodine-water. The material and the fixative may be mixed to- 

 gether at once or upon the cover-glass, which merely requires a 

 smear. When fixed and dried the preparation must be thoroughly 

 hardened. This may be done by leaving the preparations in 

 the iodine solution tor a day, and then, after washing in water 

 and weak spirit, keeping them in alosolute alcohol for one or two 

 days. The time required for hardening may be diminished by 

 repeatedly boiling the alcohol, and the preparations are more 

 clearly stained if they are then immersed in chloroform for a day. 

 It is always useful to pass the cover-glasses once or twice through 

 the flame. 



The preparations are best stained by means of haematein and 

 picric acid, the latter acting as a mordant. But it is essential 

 that the preparation should be thoroughly fixed and hardened ; 

 they may then be treated with a saturated aqueous solution of 

 picric acid for ^-3 hours ; the preparation is then passed through 

 water so as to wash oft' some, but not all, of the picric acid. For 

 staining, an alkaline solution of haematoxylin is used. It would 

 not appear, however, that the foregoing staining was more ad- 

 vantageous than that with aniline, of which the following were 

 successfully employed : phenolfuchsin, alkaline iriethylen-blue, 

 Gram's method, and also gentian-violet in carbolic acid, water, 

 glycerin, i per cent, acetic acid, and i per cent, iodide of potash. 



If the aniline dyes are used the preparation should be over 

 stained and then difterentiated by some decolorant ; if Gram's 

 method be adopted alcohol must be used ; but for other stains a 

 mixture of equal volumes of glycerin and water was found to give 

 the best results. As soon as the desired degree of decolorization 

 is attained the preparation is washed in water, dried in the air, 

 and mounted in balsam, styrax, or dammar. 



The grana or microsomes were best brought out by staining 

 with some aniline dye and then difterentiating with 2 per cent, 

 acetic acid. 



Spores are very easily stained by treating the preparation with 

 boiling phenolfuchsin and then washing out in 4 per cent, sul- 

 phuric acid. 



The yeasts used for these observations were natural cultivations 

 of ordinary bottom yeasts. The yeast was shaken up with dis- 

 tilled water and then, after settling, the fluid decanted oft'. The 

 sediment, after having been thus treated several times, was kept 

 for the observations. — Ccnt7-albl. f. Bakteriol. u. Pa?-asitenk.^ 

 xii, j8q2, pp. 337 50. 



Sterilization of Water by Pressure. — MM. Rouart, Gen- 

 este, and Herscher have constructed an apparatus for sterilizing 



