1899] MICROSCOPICAL JOURNAL. 375 



diaphragm and carrier for stop, $5 ; the stops and colored 



glasses in brass box, $3. Total, $21. 

 # 



MICROSCOPICAL MANIPULATION. 



Preparing Nutrient Agar-Agar. — Dr. T. Yokote, in the 

 Centralblatt fur Bakteriologie, describes a method for pre" 

 paring nutrient agar-agar for culture purposes, that can be 

 carried out without special apparatus, or loss of time and 

 material as follows : 



Fat sinew-free beef, 500 grams, cut into small pieces, is 

 shaken with a liter of distilled water, in a flask. After a 

 thorough agitation the flask is put on the sand-bath and 

 heated, at first gently, but with gradually increasing in" 

 tensity until a lively boil is reached. After boiling for one 

 hour and a half, the flask is removed and the liquid filtered 

 while hot, through paper. To the filtrate add 15 gm. of 

 agar in shreds, return to the sand-bath and boil for about 

 one hour. Remove and add 10 gm. pepton and 5 gm. com- 

 mon salt, agitate until dissolved and then neutralize the li- 

 quid with a concentrated solution of sodium carbonate, or 

 potash lye. The soda should be added until a piece of lit- 

 mus paper plunged into the broth shows a weak but dis- 

 tinct alkaline reaction. Let cool down to the neighborhood 

 of 50 degs. C. (122 degs. to 125 degs. F)., add the white of 

 2 eggs, and agitate thoroughly (on the thoroughness of the 

 agitation depends the rapidity of the subsequent filtration). 

 Return the vessel to the sand bath and heat until the tem- 

 perature of the sand in the neighborhood of the flask 

 reaches 110 degs. C. (230 degs. F.), and mantained at this 

 point for from 1 to 2 hours. (The regular maintenance of 

 the temperature at this point has also considerable influ- 

 ence on the character of the product). During the boiling 

 the water lost by evaporation must be restored by frequent 

 additions of boiling water. After boiling the requisite 

 length of time filter through a moistened pleated filter 

 This operation, when everything goes right, ought not to 

 take more than 5 minutes, but it is frequently very slow 

 taking sometimes as much as 6 hours. 



