Page:Defensive Ferments of the Animal Organism (3rd edition).djvu/207

 in many places, and here part of the liquid became enclosed by capillary action, thus forming a kind of communication between the contents of the tube and the liquid outside. From these observations it follows, that the toluol should never be introduced before the dialysing tube has previously been immersed in the 20 c.c. of water, in which case the quantity of toluol added can be accurately controlled, and care can be taken that both the inner and outer surfaces of the tubes shall project at least 0.5 c.c. over the toluol layer. Moreover, only wide-mouthed Erlenmeyer flasks should be used.

Then the flasks are placed in an incubator at a temperature of 37°C. At a higher temperature the ferments would be destroyed, and at a lower temperature the decomposition would be too slow.

After about sixteen hours the experiment is stopped. A thick layer of toluol must still be found upon the contents of the tubes, as well as on the surrounding liquid, at the end of the experiment. The Erlenmeyer flasks, carefully numbered, are best arranged in no special order. Then the tubes are taken out of the flasks, and placed, right up to the end of the experiment, into empty Erlenmeyer flasks. In withdrawing the tubes one at the same time effects a uniform mixing of the dialysate. Particular care must be taken to avoid a source of error that often arises at this point, which is, that if the flask has been supplied