Not long ago, in a review of certain features of the so-called Abderhalden reaction, attention was directed to the accumulating evidence of its nonspecificity.1 The original claims made for the reaction have given rise to extensive series of investigations on the proteolytic enzymes of blood. The fundamental question is whether protein-splitting capacities develop in the blood in response to the introduction of foreign protein so that the serum will cause digestion when it is allowed to act on the protein injected. Much of the controversy has centered in the efficiency of the experimental technic employed. For this reason nearly all recent investigators in this domain have attempted to apply methods which will be reasonably devoid of sources of error and free from the bias of personal judgment.
At the University of Pennsylvania, Hulton2 has lately tested the response of rabbits to a number of well-characterized isolated proteins, including