MEDIA FOR GROWING TRICHOPHYTA, ETC. 53 



medium the diphtheria bacillus forms large white colonies after incubation 

 for twenty-four hours. The growth of many organisms is inhibited. 



Media for growing Trichophyta, Moulds, etc. 



1. Beer Wort Agar. — Take beer wort as obtainable from the brewery 

 and "dilute it till it has an s.g. of 1100. Add 1'5 per cent, of powdered 

 agar, and heat in the Koch till it is dissolved (usually about two hours 

 are necessary). Filter rapidly and fill into tubes. Sterilise in the Koch 

 for twenty minutes on three successive days. If the medium is heated too 

 longit loses the capacity of solidifying. 



2. Sabouraud's Media. — Sabouraud recommends the following 

 media, the first being that most frequently used : — 



(1) Pure tap water 1000 c.c. 



Maltose ("brute de Chanut") . . . 40 grms. 

 Peptone (" granulee de Chassaing") . . 10 ,, 

 Agar 18 „ 



(2) Pure tap water 1000 c.c. 



Glucose ("massee de Chanut") . . . 40 grms. 

 Peptone ("granule^ de Chassaing") . . 10 ,, 

 Agar 18 ,, 



In order to secure uniformity of results over as long a series of observa- 

 tions as possible, it is advisable to make up these media in large 

 quantities, say three litres at a time in a five-litre flask. The agar is 

 put to soak in the water for an hour, the other ingredients are added and 

 dissolved by gradually heating to 120° C. in an autoclave. The medium 

 is then thoroughly mixed by stirring and rapidly filtered through papier 

 Ohardin (Cogit, 36 Boulevard Saint Michel, Paris). For this purpose, 

 SabouTand recommends that ten 500 c.c. flasks should be fitted with 

 funnels and filtration simultaneously carried on in the whole series ; 

 whenever in any one of the flasks the filtrate begins to pass only in 

 drops, a new filter paper is substituted. In this way the three litres of 

 medium can be filtered in a few minutes. We have found that the pro- 

 cedure can be simplified without apparently affecting the efficiency of the 

 medium, by dissolving the agar and sugar in one flask, and the peptone in 

 another. The contents of each are filtered and the two filtrates are then 

 mixed ; in this procedure only two or three filter papers are required for 

 the rapid filtration of a large quantity of the agar and sugar moiety. If 

 filtration in a number of flasks is practised, the contents of all are 

 mixed and then distributed in 6 x § inch test-tubes (plugged with non- 

 absorbent cotton) and sterilised by one exposure in the autoclave at 

 120° C. — the temperature being very gradually raised. These tubes are 

 used for the primary inoculations, and during incubation, which is 

 necessarily prolonged and usually carried out at 22° C. , should be placed 

 in a covered glass jar the lid of which is kept slightly raised at one side 

 with a pad of wool to permit the access of a certain amount of air, — 

 by this device undue drying of the medium is at the same time prevented ; 

 the inoculated tubes should not be covered with rubber caps. The 

 study of the characters of the large colonies of trichophyta, etc., is best 

 carried out with media distributed in 250 or even 500 c.c. Erlenmyer 

 flasks in which the requisite surface of medium with a, suitably moist 

 atmosphere is obtained. 



