THE PREPARATION OF CULTURE MEDIA 



35 



levelled ice-plate may be dispensed with ; in all other 

 respects the details of manipulation are the same as 

 were described for the pouring of the plates. 



Tube method. Another modification of the original 

 method of plate- culture consists in taking rather larger 

 tubes of gelatine, melting the latter and introducing the 

 material for investigation directly into the tube. The 

 cotton-wool plug is then replaced and the gelatine 

 agitated ; this must be done gently, to prevent the for- 

 mation of air-bubbles. An india-rubber cap is then 

 drawn over the cotton-wool stopper, and the tube is 

 carefully rotated in a horizontal position in iced or 

 cold water so as to bring about the solidification of the 



FlG. 8. ESMARCH TUBE-CULTUKE. 



, india-rubber cap ; b, b, b, longitudinal line drawn on glass ; c, c, c, transverse 

 lines on glass to facilitate the counting of the colonies. 



gelatine in an even layer over the internal wall of the 

 tube. On keeping the tube at 18-22 C. the colonies 

 develop in the same manner as in the case of the plates 

 and dishes. This method was devised by Esmarch, and 

 the accompanying figure shows the appearance of such 

 a tube. This method, in consequence of its extreme 

 simplicity, may sometimes be employed with great ad- 

 vantage, w r hilst a modification of it is most conveniently 

 adapted for the cultivation of anaerobic micro-organisms 

 in colonies (see p. 40). 



Whichever of the above methods has been adopted, 

 the colonies, as soon as they have sufficiently developed, 

 are in the first instance examined under the microscope 

 to ascertain what characteristic appearances they pre- 

 sent, which will enable them to be subsequently reiden- 



