ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1^29 



Differentiation of Streptococci.*— H. W. Crowe finds valiial)le 

 assistance in dilferentiaring certain streptococci by means of Dorset's 

 egg medium, to which nentral-red in the proportion of • 005 p.c. is 

 added as indicator. The chief points are the colour and shape of the 

 colony, and the effect (if any) on the surrounding medium. 



(2) Preparing- Objects. 



Demonstrating Presence of Protozoa in Soils. f — C. H. Martin 



mixes a small quantity of the soil with an equal volume of picric acid. 

 The mixture is then placed in a wide dish, carefully stirred and allowed 

 to stand. This allows bacteria, diatoms, and protozoa to come to the 

 surface. Coverslips are then floated on the surface, and afterwards 

 placed in corrosive. The shps are then handled as ordinary smears, 

 and afterwards stained for some time with strong acid-hsemalum, fol- 

 lowed by eosin. Clean preparations, showing large numbers of amcebse 

 and flagellata, are obtained. 



(3) Cutting-, including- Embedding- and Microtomes. 



Berlin-blue Injection Mass.| — B. Mozejko finds that the presence 

 of sugar prevents clotting or precipitate in injection masses of Berlin- 

 blue gelatin. The author leaves 5 grm. gelatin in 20 grm. distilled 

 water to macerate, and afterwards dissolves it on a water-bath. Mean- 

 while 5 grm. of ordinary sugar are dissolved in 10 grm. of saturated 

 Berlin-blue solution. This is immediately added to the gelatin ; a per- 

 fectly homogeneous solution results. To this are added 100 grm. of 

 saturated Berlin-blue solution. The mass is then filtered. 



The author then advises that in order to prevent the decolorization 

 of the pigment, the injected preparation should be fixed in the follow- 

 ing solution. Formalin (40 p.c.) 10, alcohol (70 p.c.) 90, nitric acid 5. 



After fixation the preparations are to be removed to alcohol, which 

 should be twice changed. 



Recent Histological Methods. § — S. v. Apathy gives an account of 

 the methods of embedding, section-cutting, and mounting employed in 

 his laboratory. The paper consists mainly of a recapitulation of 

 processes previously described, but contain much valuable information 

 upon a large number of minor points. In a short abstract it is only 

 possible to deal with one of the many aspects of the subjects discussed, 

 and possibly the most suitable for reference is the new oil-gelatin method 

 of embedding, by means of which undistorted preparations of inter- 

 cellular matrix may be obtained. The tissue is placed in glycerin-water 

 (1:1) and to this is added an equal volume of gelatin solution. This is 

 left for at least 24 hours in a thermostat at 40° to allow the gelatin to 

 permeate. The subsequent procedures consist of thickening of the 

 gelatin, passing through upgraded alcohols, drying over calcium chloride, 

 bardening in absolute alcohol, and replacing the alcohol by terpinol. 

 The gelatin block may then be treated as celloidin. 



* Proc. Roy. Soc. Med. (Path. Sect.) vi. (1913) pp. 117-25 (1 col. pL). 



t Nature, xci. (1913) pp. 111. 



: Zeitschr. wiss. Mikrosk., xxix. (1913) pp. 516-22. 



§ Zeitschr. wiss. Mikrosk., xxix. (1913) pp. 449-515. 



