MICROSCOPICAL TECHNIQUE. 189 



specimens after washing can be put in 93 per cent, alcohol, and if 

 the washing has only taken a short time they may be left in it from 

 twelve to twenty-four hours. Remaining in the fluid for three or 

 four days at room temperature does not injure the specimens, but 

 rather facilitates the subsequent staining. Karyokinensis may thus 

 be more frequently observed. Carmine preparations, also haema- 

 toxylin and methylene blue, are efficient staining re-agents 



The hardening in formol-Miiller is especially suitable for bone 

 decalcified with phloroglucen and nitric acid. For naked-eye spe- 

 cimens formol-Miiller is also useful. Besides blood, fat, cartilage, 

 and bone are thus well differentiated, and pigments, colloid mate- 

 rial, etc., are also well fixed. Haemorrhagic nephritis, fatty 

 degeneration of the heart, etc., are well prepared by this method. 

 The colouring of the grey and white matter of the brain is very 

 satisfactory. Weaker alcohol (60 per cent.), to which formol (i per 

 cent.) has been added, is a good preservative fluid after formol- 

 Miiller ; also a combination of alcohol, glycerine, water, and 

 formol (i per cent.) may be employed. Embedding in gelatine, to 

 which I per cent, formol has been added, is successful. For the 

 preservation of tissues for demonstration i per cent, formol is very 

 useful. The specimens may be dipped in this solution, and then 

 wrapped in cloths soaked in it. Formol is very valuable as a dis- 

 infectant, particularly for washing the hands after a post-mortem 

 examination. The vapour is irritating, and therefore people should 

 not remain in a room where it is present for only a short time. — 

 Brit. Med. Journal. 



Growth of Diatoms. —Mr. G. C. Whipple has carried on a 

 series of experiments on the culture of different kinds of diatoms, 

 and finds that an abundant food-supply is not the only condition 

 favourable for their rapid increase ; the temperature, the amount 

 of light, and other factors influencing their growth. In common 

 with all other chlorophyllaceous plants, diatoms will not grow in 

 the dark, while, on the other hand, bright sunlight also kills them. 

 The intensity of the light below the surface of the water being 

 affected by the colour of the water, diatoms are found most abun- 

 dantly in light-coloured water. Different genera, however, exhibit 

 differences in this respect. Melosira does not require so much 

 light as Synedra. The weather has a marked influence on the 



International Journal of Microscopy and Natural Science. 

 Third Series. Vol. VII. o 



