60 BACTERIOLOGY 



serum is only used in the solid state, and is principally 

 adapted for surface or streak cultures (Strichcultureri). In 

 order, however, to render it available for plate cultivation, 

 Hiippe mixes it with an equal quantity of a warm solution of 

 agar ; and it may also be suspended in gelatine. Unna in- 

 creased the coagulability of blood serum by rendering it 

 strongly alkaline, in order to add it to gelatine or agar. 

 This medium has special excellences for a number of micro- 

 organisms. 



The albumen taken from plovers' eggs which have been 

 previously sterilised with 1 per 1,000 corrosive sublimate 

 may be inoculated and then dried over sulphuric acid under 

 the receiver of an air-pump. Plates so inoculated can be 

 kept for a considerable time if preserved in a sterile place, 

 and when laid in a moist chamber there appear on the thin 

 dry transparent film of albumen variously shaped areas of 

 different sizes, which may be transferred to other culture 

 media. Plover's egg albumen may also, like blood serum, be 

 mixed with gelatine or agar, and so used for plate cultures. 



The micro-organisms can be transferred to other media 

 from agar and serum plates in the same way as from gela- 

 tine, and the appearances presented by them in their growth 

 observed. 



Cultivation of anaerobic micro-organisms. For the culti- 

 vation of anaerobic microbes, that is, those which grow with 

 a scanty supply of oxygen, or when it is totally excluded, 

 an entire series of methods have been devised, of which the 

 following are a few. 



The most direct plan is to introduce at once into the 

 nutrient medium such substances as will extract the oxygen 

 present, a result which is attained by adding to nutrient 

 gelatine 2 per cent, of grape sugar or O'l per cent, of 

 resorcine, or to liquefied nutrient agar J per cent, of formic 

 acid or of sodium sulphindigotate. 



