1404 



Journal of Applied Microscopy 



The dilution in the test reduces the amount considerably below that neces- 

 sary to retard the growth of B. coli and B. typhosus, but is still sufificient to pre- 

 vent the growth of many species which would ferment the broth and interfere 

 with the test. After inoculation, the bottles are placed in an incubator at 38°C. 

 for twenty hours. At the end of this time, if B. coli be present, there should be 

 a slight bead on the surface. Immediately on removing from the incubator, 

 give the bottle one quick, hard shake, and set it up in front of a window. The 

 gas, if B. coli be present, will now separate from the liquid and rise slowly to the 

 top, giving the same appearance as when a bottle of highly carbonated water is 

 opened. This appearance is quite characteristic. The pressure of the liberated 

 gas is frequently sufficient to blow the stopper out of the bottle. We always 

 plate out a sample showing positive indications and test to confirm the diagnosis, 

 and in over 75 per cent, of such samples we have found B. coli to be the 

 organism responsible for the fermentation. On the other hand, we have plated 

 out many hundred negative tests, and have yet to find one in which B. coli was 

 present. 



A Fermentation Tube Adapted to Rapid Handlino in Routine Work. — 

 In 1897, when we first began making routine tests for B. coli, we found that the 

 usual type of fermentation tube, with a base, a large bulb, and a constriction at 

 the bend, was not suited to rapid work, accordingly I had some tubes made 

 omitting these features. 



These tubes have given such general satisfaction 

 in our laboratory, that I hope the following descrip- 

 tion and illustration will be of some value to others 

 in the same line of work. The shape and dimen- 

 sions of the tube are shown in the sketch. The 

 tubes, when filled about as in the sketch, are set in 

 a wire basket in rows, cotton wool being placed in 

 the bottom for them to rest on. We use baskets 

 3x5 inches, and 5 inches deep ; these will hold ten 

 tubes in a row, and by putting in layers of cotton 

 wool, three tiers can be placed in a basket. In this 

 way, thirty tubes occupy about as much space as 

 five or six of the ordinary style of tube would 

 occupy, and can be handled as a unit in steriliza- 

 tion, etc. The open arm of the tube is sufficiently 

 long to hold all of the liquid when it is forced out 

 of the closed arm, without wetting the cotton plug. 

 Determinations of the volume and composition of the gas are made as easily and 

 accurately as in the old style of tube. We have all of our tubes, test tubes 

 included, made without lips, as we think it tends to decrease the breakage, and 

 make the tubes pack better in baskets. The abolishment of the bulb and con- 

 striction at the neck also makes cleaning somewhat less of a grind. 



Lawrence Experiment Station. " STEPHEN DeM. Gage. 



