PEPTONrSED MEAT JELLY. 75 



larger dimensions, fitting as a collar, and leaving an interspace be- 

 tween the two funnels, which acts as a water chamber. Hot water 

 is placed in this chamber, and its heat maintained by the application 

 of a Bunsen burner to a copper diverticulum connected with its 

 cavity. The filter paper is washed with boiled distilled water, to 

 remove any fine separable particles from it ; and the gelatine solution 

 first passed through it is reserved for a second filtering, so as to 

 secure a perfectly pellucid filtrate. During the process of filtra- 

 tion the funnel is kept covered with a glass plate or bell, to prevent 

 ingress of dust from the air. The filtrate is received into sterile 

 glass flasks, stoppered with sterile cotton wool plugs. These are pre- 

 pared as follows : — The flasks (one quarter litre) are thoroughly washed 

 and dried, and then plugged with cotton wool. The stoppered empty 

 flasks are then submitted to a dry heat of 170 C. for an hour, which 

 effects their complete sterility. The plug is then removed from the 

 mouth of one of these sterile flasks, and held with a pair of catch 

 forceps, so that it touches no other object, its lower aspect at the same 

 time being directed downwards, so as to avoid deposition upon it of the 

 dust particles settling from the air. The flask is placed below the filter, 

 and the gelatine is allowed to pass into it till it is about one-quarter full. 

 It is then quickly plugged, and another flask introduced in its place. A 

 flask so charged with gelatine broth is called a stock-flask. The flasks, 

 thus charged with the clear filtrate, and at once plugged with cotton, 

 are then placed in the steriliser and steamed for twenty minutes. If 

 they are as much as half full, there is danger of the contents rising as 

 high as the cotton wool plug, whence during the steaming process a 

 quantity of particles may be washed down, which interfere with the 

 perfect transparency of the nutrient jelly. If the filtrate is not per- 

 fectly clear, it must either be refiltered, or it must be clarified with 

 egg albumen. This is effected as follows : — The white and shell of an 

 egg are beaten up into a frothy mass, and added to the whole supply 

 of turbid gelatine broth. This is then placed in the steam steriliser, 

 and steamed until coagulation of the egg albumen takes place. By 

 the action of heat all the egg albumen is precipitated, and it carries 

 down with it the fine particles suspended in the broth, and leaves, 

 when separated by filtration, a perfectly clear nutrient substance. At 

 the end of the third day's steaming, the gelatine broth, now in stock- 



