Page:Defensive Ferments of the Animal Organism (3rd edition).djvu/173

 contains none of the active ferments capable of decomposing albumen. Should we detect the presence of peptones, we may be certain that some decomposition of the albumen has taken place. In our special case the fluid to be tested is blood serum. It is obvious that the method is exactly the same, when we test, for their capacity of decomposing albumen, such substances as cerebro-spinal fluid, lymph, or extracts from various organs—e.g., juices obtained by means of high pressure.

Dialysing Tubes.—The result of tests for albumen-decomposing ferments by the dialysation process depends in the first place upon the quality of the membrane used. The latter must above all answer two requirements. First of all it must be absolutely impermeable to albumen, and further, evenly permeable to decomposites of albumen. If the tube allows albumen to pass through it, the latter may be mistaken for peptones, unless we apply special tests for albumen. Should dialysing tubes be used which allow peptones to diffuse through at a variable rate, then we should be at a loss in our judgment upon the results of a test, because, as will presently be shown, a control test of the fluid to be tested must always be made, without the presence of albumen, and the results of this test be compared with those of the tests in which albumen has been mixed in the dialysing tube with the fluid under research. Should one