1899] MICROSCOPICAL JOURNAL. 375 



diaphrag-m and carrier for stop, $5 ; the stops and colored 

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



MCEOSCOPICAL MANIPULATION. 



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

 Centralblatt fur Bakteriolog-ie, describes a method for pre- 

 paring- nutrient ag-ar-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 

 thoroug-h 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, throug-h 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 plung-ed into the broth shows a weak but dis- 

 tinct alkaline reaction. Let cool down to the neighborhood 

 of 50 deg-s. C. (122 degs. to 125 deg^s. F)., add the white of 

 2 eggs, and agitate thoroughly (on thethoroug-hnessof 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 deg-s. F.), and mantainedat this 

 point for from 1 to 2 hours. (The reg-ular 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 

 leng-th of time filter through a moistened pleated filter 

 This operation, when everything- goes rig-ht, ought not to 

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

 taking sometimes as much as 6 hours. 



