J. BRONFENBRENNER 1061 



Case II (Table II). — The test proper may give a positive ninhydrin reaction and the 

 control with the serum alone negative. If all the controls accompanying the test (see Table I, 

 Thimbles 3, 4, 5, 6, and 7) give expected results, the foregoing outcome of the examination 

 of unknown serum means that it contained specific ferment which digested the given 

 substratum. 



Case III (Table II).— A third possible outcome of the test may be that the dialysate 

 from the thimble containing the serum alone (control), as well as dialysate from the test 

 proper, in which the thimble contained both the serum and the substratum, both give a 

 positive ninh>'drin test. In order to interpret this result correctly, it is necessar.\' to establish 

 the cause of the presence of ninhydrin-reacting substances in the control dialysate, for ac- 

 cording to the cause the interpretation may vary. 



Assuming that the technique was perfect, so that no protein could have been introduced 

 in the dialysate by faulty manipulation (as, for example, soiling the outside of the thimble 

 with serum while introducing it in the thimble, or contaminating the distilled water in the 

 flask with saliva' while introducing it by means of a pipette, or depositing organic matter on 

 the outer wall of the thimble by handling it with the fingers instead of with forceps, etc.), 

 there are two other possible reasons for the presence of protein in this dialysate: either the 

 thimble was permeable to unchanged serum or the serum contained dialyzable products be- 

 fore the test. 



Although the thimble was supposed to have been tested and found to have been imper- 

 meable to natural protein, it is still possible that in further manipulation it might have been 

 punctured. In order to establish this point, it suflices to test the dialysate for the presence of 

 coagulable protein, and if it contains unchanged serum, the thimble must be discarded and 

 the whole test repeated with a new thimble. If, however, the dialysate does not contain 

 coagulable protein, it means that the thimble was not punctured and that the substances 

 giving the ninhydrin test are of the nature of dialyzable derivatives and must have been 

 present in the serum before the test. 



Having established that the ninhydrin test on control dialysate is due to the presence of 

 dialyzable protein-split products in the serum, one must compare the intensity of this re- 

 action with that obtained with dialysate from the thimble containing both serum and 

 substratum. If the latter is decidedly more intense, the outcome of the reaction may still be 

 considered satisfactory. If, however, the intensity of reaction in both cases is nearly equal, 

 the test must be repeated.^ 



In cases, however, where it is impossible to obtain the specimen of blood free from dialy- 

 zable ninhj'drin-reacting substances (as, for example, if the patient is having a high temper- 

 ature, or in general in cases where there is marked active katabolism of protein), it is neces- 

 sary to resort to a special method suggested by Schlimpert and Issel.^ The serum is dialyzed 

 against running salt solution, until free from dialyzable ninhydrin-reacting substances, and 

 only then is it examined according to the usual procedure. 



Case IV (Table II). — It is possible, finally, that the test of unknown serum will show a 

 positive ninhydrin reaction with a control dialysate (serum alone), and a negative reaction 

 with dialysate of the test proper (serum and substratum). This result is to be interpreted 

 as follows: 



' According to Abderhalden, saliva even in dilution i : 1,000,000 in water gives a positive ninh}-- 

 drin test. 



2 Abderhalden, E.: Abwehrfermente (4th ed.), p. 289. Berlin, 1914; Bisgaard, A., and Korsbjerg, 

 A.: Deutsche med. Wchnschr., 40, 1367. 1914. 



jPorchownick, T.B.: Centrahl.f. Gyniik., 37, 1226. 1913; Abderhalden, E., and Wildermuth, P.: 

 Miinchen. med. Wchnschr., 61, 862. 1914. 



