18 THE AMERICAN MONTHLY [Jan 



the cold bouillon to a paste and then gradually add the bal- 

 ance of 500 cc. thereof, and boil until solution — which 

 quickly takes place — is complete ; add the balance (500 

 cc. ) of the bouillon ; stir in the whites of two egg» and 

 boil until the egg albumin is coagulated and rises to the 

 surface leaving the clear solution beneath, and then filter, 

 as before. As, however, the agar <uin be made from the 

 tiesh-water almost as readily and quickly as from the bouil- 

 lon there is little use for previoubly prepared bouillon. 



Meat extract can also be substituted for the flesh-water. 

 Formerly I used from 20 to 30 cc. of Valentine's meat 

 juice per liter, but more recently I use but 10 to 15 cc. 

 which quantity I find suflBcient. I prefer Valentine's to 

 other extracts that I have tried as it makes a lighter color- 

 ed agar and seems to be free from resistant spores, as no 

 more care is required in the sterilization of the media 

 made from it than from meat itself. If 10 cc. of meat ex- 

 tract (or meat juice as Valentine terms it), be added to 500 

 cc. of water and substituted for the flesh-water the pro- 

 cess is the same as with the latter, save that egg albumin 

 must be added to clear the medium if it be desired to fil- 

 ter before sterilization. Meat extract, is more convenient 

 than meat for making media, but some organisms do not 

 seem to thrive so well u})on the media thus made. 



The precaution of first moistening the agar and pep- 

 tone with a small quantity of cold water or cold bouillon, 

 as the case may be, and rubbing to a smooth paste free 

 from lumps, must not be omitted. If stirred directly into 

 a hot solution — and to a less extent if stirred directly into 

 a large quantity of cold water, without previous moist- 

 ening — the agar rolls up into little lumps and is almost 

 as difficult of solution as the finely cut pieces of shred agar. 



If a meat press is not at hand the flesh-water can be 

 made in the ordinary way either by macerating finely 

 minced meat in cold water for a few hours, or by digest- 

 ing for a shorter time at a higher temperature. 



