ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 623 



egg-white being drawn up into a sterile Pasteur pipette.) The result- 

 ing mixture is then shaken vigorously for five or ten minutes, until the 

 linu id is homogeneous and free from lumps of albumin. One then 

 prepares a sufficient quantity of 2 ■ 5 p.c. neutral agar, to which ■ 2 c.cm. 

 of a solution of caustic soda (10 parts per 100) has been added per litre. 

 One part of the serum-egg mixture is then added to three parts of the 

 agar mixture (heated to 100° C. and then cooled to 50° C), the result- 

 ing medium being then sloped in the usual way. 



The new medium has given excellent results in the author's hands, 

 both with cerebro-spinal fluid and with naso-pharyngeal exudates con- 

 taining the meningococcus. 



(2) Preparing Objects. 



Preparation of Crystals.* — R. Pettigrew gives the following 

 method of preparing crystals referred to in " Melting Crystals," which 

 appeared in vol. ii. of the " Micrologist." 



Camphor monobromide crystals are added to natural Canada balsam, 

 the mixture being gently heated in a test-tube, and crystals added suc- 

 cessively until, on cooling, the mass solidifies ; about three times as much 

 of the camphor as of balsam will be found necessary. When required 

 for preparing slides, melt the mass by gently warming over a spirit- 

 lamp, take a drop out with a warm glass rod, put a drop about a quarter 

 of an inch on a warm slip, and cover and press down with a warm cover- 

 glass. When cool scrape away the excess and ring with gold-size. When 

 warmed to about 70° C. — by holding a lighted match uuderneath the 

 reversed slide — the material will melt and, on cooling, gradually 

 crystallize. If the match used for heating be held so that all but just a 

 little at one edge is melted, the growth of crystals will start from the 

 unmelted portion more quickly than if all be melted. By arranging 

 the amount of camphor monobromide, the time of growth may be 

 shortened or lengthened at will, but, generally, best* results are obtained 

 from a very thin layer, and which takes about one minute to start growth. 

 If some tiny air-bubbles be left in on mounting, they are of value, as 

 the growth, on touching the air-bubble, will go off with a rush, push- 

 ing the air-bubble in front of it in a zig-zag line. It is not necessary to 

 make different tubes of material. If quick growth be required, choose 

 a medium growing sample, and add some crystals of monobromide to a 

 drop on a slide ; if a slow growing sample, a little balsam. 



Preparation of Chick Embryos. f — A. Flatters gives the following 

 method of preparing, staining, and mounting chick embryos. The eggs 

 are taken out of the incubator one at a time, the pointed ends cracked, 

 and the shell picked off sufficiently to allow a clear view of the embryo. 

 The bottom half of the shell, containing the embryo, is now placed 

 in a dish of water kept at 105° Fahr., and allowed to rest on the bottom 

 of the dish, the broken edge of shell and exposed embryo standing above 

 the water line. The tissues of attachment are now severed and the 



* Micrologist, iii. (1915) p. 22. 



t Micrologist, iii. (1915) pp. 17-21. 



