88 CLINICAL BACTERIOLOGY. 



manipulate further the colonies of a single species of 

 bacteria. 



The particulars of Kochs method of plate-making are as 

 follows : With the aid of a platinum wire melted into a 

 glass rod (Fig. 17), a small amount of the material to be 

 examined is introduced into a gelatin-tube whose contents 



Fig. 17. Platinum wire swaged into brass wire and reversible for transportation 

 (as devised by Dr. J. H. McCollom) : a, Closed ; b, open; c, the same with end bent 

 at a right angle, for picking up colonies in test-tube ; rf, the same in operation (Ernst). 



have previously been liquefied by immersion in water at 

 a temperature of from 30 C. (86 F.) to 40 C. (104 F.). 

 The platinum wire must, of course, have been heated in the 

 flame of a Bunsen burner or of a spirit-lamp before being 

 used, in order to be freed from germs that may have been 

 attached to it. When the material to be examined contains 

 many bacteria, it is sufficient to insert the extremity of the 

 heated wire, but. if the number of bacteria is small, it is 



Fig. 18. Platinum wire twisted into a loop. 



better before heating the wire to twist it into a loop in order 

 that it may take up more of the material. (Fig. 1 8.) If a solid, 

 compact substance is to be examined with regard to the pres- 

 ence of bacteria, it is, by means of a glass rod sterilized in 

 the flame and subsequently cooled, broken up in a watch- 

 glass similarly treated ; it is then rubbed up with sterile 



