7 2 SOLID CUL TIVA TION MEDIA . 



variety of organisms thus met. This form of soil is specially adapted 

 for the growth of the various species of moulds — Aspergilli, Mucores, 

 and Penicillin. 



Summary of Process for preparing Sterile Bread Paste. 



First Day. — Place ten grammes bread crumb and 2-5 c.c. water in a 

 glass flask. Plug with cotton wool. 

 Steam flask at 100° C. for thirty minutes. 

 Second Day. — Repeat steaming for thirty minutes. 



(C.) Cultivation in Sterile Nutrient Jelly. 



43. In the nutrient soils already described we have had to deal 

 with an opaque substratum, on which only the surface appearances of 

 the cultivated organism can be distinguished. In order that the more 

 intimate relations and tendencies of the growth may be observed, it 

 is desirable that some material should be devised which combines 

 sufficiently nourishing qualities with solidity and transparency. 

 These conditions are realised by the peptonised meat jelly devised 

 by Koch, in which a highly concentrated meat infusion is rendered 

 solid by the admixture of gelatine, its nutrient qualities enhanced by 

 the addition of peptones, and its perfect transparency ensured by 

 careful filtration, or, if need be, by clarification. The method of its 

 preparation is as follows : — To two pounds of finely minced lean meat 

 (pork or beef by preference) are added two litres of distilled water. 

 These are well stirred together, and allowed to stand for twenty-four 

 hours in a cool place. The fat, which separates and floats on the 

 surface, is then removed with a creaming ladle or clean filter paper, 

 and the residue is poured into the cavity of a screw press (Fig. 31), 

 lined with a fine cotton cloth, through which the liquid portions 

 are strained, and collected in a large glass flask. The mass of meat 

 thus left is closely wrapped in the piece of cloth, and is subjected to 

 repeated pressure in the screw press, so as to deprive it of all remain- 

 ing liquid. 



By this means a turbid red broth is obtained, which should 

 measure two litres. If it measure less than this, add some distilled 



