THE USE OF THE OEDINARY CULTUKE MEDIA 55 



culture, the resulting growth is said to be a " sub-culture " of 

 the first. Manipulations involving the transference of small 

 portions of growth either from one medium to another, as in the 

 inoculation of tubes, or, as will be seen later, to cover-glasses for 

 microscopic examination, are effected by pieces of platinum wire 

 (Nos. 24 or 27 Birmingham wire gauge — the former being the 

 thicker) fixed in glass rods 8 inches long. 1 If platinum wire is 





Fig. 12. — Tubes of media. 



a. Ordinary upright tube. > 



Fig. 11.— Apparatus which may >>. Sloped tube, 



be used for filling tubes. The «■ ^Srotai 



apparatus explains itself. The 

 indiarubber stopper with its 

 tubes ought to be sterilised 

 before use. 



not available an excellent substitute, — especially for students' 

 work,— is found in "resistance wire," No. 25 B.W.G. This is 

 best mounted in an aluminium handle. Every worker should 

 have three wires. Two are i\ inches long, one of these being 

 straight (Fig. 13, a), and the other having a loop turned upon it 



1 Aluminium rods are made which are very convenient. The end is split 

 •with a knife, the platinum wire is inserted and fixed by pinching the 

 aluminium on it in a vice. , 



