io62 ABDERHALDEN'S REACTION AND "PROTECTIVE" FERMENTS 



It is possible that the failure to obtain the ninhydrin test in the dialysate from the test 

 proper (serum and substratum) could be due to impermeability of the thimble to dialyzable 

 products. This is ascertained by thoroughly washing the thimble and testing it subsequently 

 for permeability to silk peptone. If the thimble is found to be impermeable, the whole test 

 has to be repeated. If the thimble is found permeable, it is evident that digestion did not 

 occur during the incubation period, because the serum did not contain specific ferments. 



As to determining the reason for the positive ninhydrin test obtained with the control 

 dialysate, one most proceed as in case III just described, and determine whether the thimble 

 was letting through unchanged serum. If the coagulation test on the dialysate is positive, 

 the thimble should be discarded. If the thimble is not punctured, the ninhydrin test must 

 have been due to the presence in the serum of dialyzable ninhydrin-reacting substances. 

 Such instances in which the serum contains diffusible ninhydrin-reacting substances, which 

 disappear upon the addition of tissue, have been described by several authors and are at- 

 tributed to the adsorption of such dialyzable substances by the substratum. 



TABLE II 



Case 



I 



II 



Ill 



IV 



Character of the Dialysate 



The dialysate from the serum alone (control) 



The dialysate from serum and substratum (test) 



The c'ialysate from serum alone (control) 



The dialysate from serum and substratum (test) 



The dialysate from serum alone (control) 



The dialysate from serum and substratum (test) 



The dialysate from serum alone (control) 



The dialysate from serum and substratum (test) 



MODIFICATIONS OF THE ORIGINAL PROCEDURE 



Experience has shown that if all the necessary precautions and controls are car- 

 ried out the results secured by the Abderhalden reaction may be of value. However, 

 in spite of all the care taken, certain errors may still occur.' Thus, for example, one 

 cannot be sure of the fact that thimbles were perfect when used for the test, even 

 though each thimble was presumably tested beforehand, and one should not consider 

 the test finished (or the results obtained final) until all the thimbles used in the test 

 are retested and found satisfactory. For it may happen that boiling a thimble to 

 render it sterile after a preliminary test of its permeability may render such a thimble 

 impermeable to peptone. On the other hand, a thimble found to be perfect in the pre- 

 liminary test may be rendered permeable to the whole serum through an unobserved 

 mechanical injury, during the subsequent handling in setting up the main test. An- 

 other, frequent source of error has been found in the use of ninhydrin as an indicator.^ 

 This color test is so easily rendered valueless by various extraneous influences that it 

 was felt desirable to replace it by some other means of detection of cleavage of pro- 

 tein. It is for these reasons that several modifications of the original procedure have 

 been suggested. Thus, Michaelis suggested a means of eliminating the thimbles.^ He 

 recommended placing the serum with its substratum in a glass tube and after a suita- 



' Abderhalden, E.: Miinchen. med. Wclmschr., 6i, 233. 1914. 



*Bisgaard, A., and Korsbjerg, A.: he. cit. 



i Michaelis, L.: Deutsche med. Wchnschr., 40, 429. 1914. 



