io6o ABDERHALDEN'S REACTION AND "PROTECTIVE" FERMENTS 



ing 20 cc. of sterile salt solution. The contents of the thimble, as well as the liquid outside, 

 are covered with a layer of toluol, and the flask covered with a clean, dry watch-glass is placed 

 in the incubator. 



After sixteen to eighteen hours of incubation the flask with the thimble is removed from 

 the incubator. The thimble is then carefully withdrawn from the surrounding fluid and placed 

 in a fresh (clean, sterile, and dry) Erlenmeyer flask and the dialysate examined for protein 

 by means of the ninhydrin test. Into a clean, dry test tube of Jena glass is placed 0.2 cc. of 

 I per cent ninhydrin solution, 10 cc. of dialysate is added, and the mixture is boiled for one 

 minute in an oil bath.^ A procedure similar to this is followed in preparing all other dialyzing 

 units. 



The second control consists in ascertaining whether the unknown serum is free of dia- 

 lyzable substances reacting with ninhydrin. This is done by placing 1.5 cc. of the serum into a 

 tested thimble and treating the latter exactly as was done in the case of the one just de- 

 scribed. After the period of incubation the dialysate should give a negative ninhydrin test, 

 if the serum is taken with all the precautions mentioned (Table I, Thimble 2). 



TABLE I 



The third control consists in ascertaining whether the substratum has retained its 

 specific properties, namely, while not reacting with normal serum its combination with 

 specific serum will result in the appearance of dialyzable ninhydrin reacting substances. It 

 is evident that such control consists of two tests — one in which the substratum is incubated 

 with known normal serum (Table I, Thimble 5), and in the other with known specific serum 

 (Table I, Thimble 3). To complete each of these control tests it is necessary to make certain 

 that the known sera used are free from dialyzable split products of protein prior to their in- 

 cubation with the substratum (Table I, Thimbles 4 and 6). 



INTERPRETATION OF RESULTS 



The results of the test are considered reliable only on the condition that all the 

 control tests performed simultaneously have given satisfactory results. As for the out- 

 come of the test of the unknown serum (Table I, Thimbles i and 2), there are, in 

 general, four possibilities: 



Case I {see Table II). — The test tube containing the dialysate from the thimble 

 with serum alone, as well as that with serum and substratum, may give negative reactions 

 with ninhydrin. If aU the precautions of the test have been followed, this result indicates 

 that there are no protein-split products in the dialysates tested, and this in turn means (ac- 

 cording to Abderhalden's conception of the test) that the serum did not contain the ferments 

 necessary to digest the substratum. 



' Abderhalden, E.: Ahwehrjermente (4th ed.), p. 225. Berlin, 1914. 



