424 MICROSCOPICAL TECHNIQUE. 



and the mixture frequently shaken at intervals until a neutral re- 

 action is shown by test papers when it is filtered. 



Simple Method of Plate-Culture. — Dr. R. Boyce, of University 

 College, describes in Public Health a simple method employed by 

 him for obtaining thin plate cultures. It consists in placing an 

 ordinary glass slide in a wide test-tube, at the bottom of which is 

 placed some moist cotton wool. After being also plugged with cotton 

 wool, the tube with its contents is sterilised, by being exposed for 

 twenty minutes to a temperature of 120*^ C. in an autoclave, or 

 for three-quarters of an hour in ordinary steam. The sterile 

 nutrient medium is kept ready for use in a siphon pipette, and can 

 readily be spread upon the slide, after being melted by warming, 

 without risk of contamination, if the tube be held horizontally 

 whilst the plug is being removed and the slide coated. The plug 

 should then be rapidly passed through a flame and replaced in the 

 tube, which ought to remain in the horizontal position until the 

 thin film of nutrient medium on the slide is set. If a rubber cap, 

 rendered aseptic by immersion in corrosive sublimate solution, be 

 then drawn over the mouth of the tube, the prepared slide may be 

 kept ready for use for an indefinite period. Inoculation is per- 

 formed in the usual way, and incubation effected in the tube. 

 Afterwards the slide can be readily examined under the micro- 

 scope, whilst the specimen can easily be fixed in alcohol and 

 stained with gentian violet if necessary. On account of the 

 simplicity, economy of material, and convenience associated with 

 this method, it appears to possess advantages over the older 

 systems. 



Estimation of Fat in Milk, by Weiss. "^—Thirty c.c. of milk 

 is introduced into a flask of 300 c.c. capacity, and then mixed with 

 3 grams of officinal sodium hydroxide solution ; light petroleum 

 (60 grams) is added in three portions, and the mixture shaken after 

 each addition until the liquid is quite homogeneous. If the last 

 portion of petroleum does not mix readily, the liquid is placed aside 

 for a quarter of an hour, after which mixing is easily brought about. 

 The emulsion may be kept without separating for a day, but after 

 adding 20 grams of alcohol, and shaking the liquid frequently, sepa- 



* Jotirn. C/iem. Soc, No. 369, 1893, P- 396? Abstracts. 



