130 
DR. P. F. FRANKLAND ON THE QUANTITATIVE ESTIMATION OF 
tube through which air has been aspirated is withdrawn from the sterile case, care 
being taken only to handle it by the extremity (B), (fig. 1). A scratch is made with a 
file intermediate between the plugs ( a ) and (6), and the tube carefully broken across. 
The second half, containing plugs (6) and (c), is carefully laid aside on a sterile 
support, whilst the first half is held between the thumb and first finger at the 
constriction, and the broken edge passed two or three times through a Bunsen flame, 
care being taken that the heat does not reach the plug. The cottou-wmol stopper of 
one of the flasks is now withdrawn, and the extremity (A) of the tube is held 
vertically over the open flask, whilst the plug is carefully pushed down by means of a 
strong piece of sterilised copper wire, introduced from behind through the broken end 
of the tube. The plug falls into the flask, and the cotton-wool stopper is replaced. 
The second half of the tube is now taken in hand, and the broken extremitv care- 
fully passed several times through the flame. The plug (c), at the extremity (B), is 
now withdrawn by means of a hooked wire, and this end also passed through the 
flame. The plug (b) is then transferred to a second flask, in the same manner as has 
been described for (ci). 
The plug of the control-tube is similarly transferred to a third flask, the cotton-wool 
plug at the back end having been previously hooked out by means of a wire, and the 
broken end passed through the flame. 
The gelatine in each flask is then agitated with the plug by means of a rotatory 
movement, which, whilst rapidly and completely disintegrating the plug, does not 
cause the gelatine to froth. In a few minutes the plug is quite broken up, in the 
case of the sugar plugs everything but the glass-wool skeleton passing into solution. 
The flask is now held almost horizontally under a stream of water, and by uniformly 
rotating it an almost perfectly even film of gelatine is spread over its inner surface. 
The successful spreading of the gelatine requires a little practice, and it is necessary 
that the stream of water should be sufficiently cold, otherwise the gelatine forms 
lumps ; on this account, in summer iced water has generally to be used. 
It is best to allow the flasks thus coated internally to remain for an hour or so in a 
cool place. They are then placed under a bell-jar, the internal air of which is kept 
saturated with moisture by means of blotting-paper soaked in water. The flasks are 
allowed to incubate at a temperature of about 22° C. for a period of 4-5 days. The 
development of the colonies takes place rather more slowly, than in Hesse’s tubes, 
which is, doubtless, due to the fact that the organisms, not being quite on the surface 
of the gelatine, must first grow up to the surface before a colony of any considerable 
dimensions can be formed. The accompanying photographs * illustrate the appear¬ 
ance of these flasks after proper incubation. The counting of the colonies is effected 
with great ease by dividing the flask with ink into segments, and holding them up 
against the light. 
* I am indebted to Mr, Carrodus for bis kindness in executing these photographs for me. 
