in later, than in the dialysation process. We remove part of the decomposition from the influence of the ferment, when we convert albumen into peptone in the test-tube. It must be our aim to maintain the peptone mixture in as high a molecular state as is possible, as experience has shown, that decomposites of too low molecularity are not attacked by some kinds of serum, which decompose more highly molecular peptones. It is very clearly shown, in this connection, that the conception of the unity of the proteolytic ferments does not correspond at all with the reality. There is not the slightest doubt, that different ferments exist for different stages of decomposition. The principal problem, in the application of the optical method to biological questions, was the elaboration of a method of dealing with highly molecular peptones, which are very closely related to the albumens.
The Application of the Optical Method.—This is very simple. 1 c.c. of serum, absolutely free from hæmoglobin, is placed in a test-tube. It must not contain any form-elements, and must be sterile. To this is added 1 c.c. of a 5 to 10 per cent. solution of peptone, prepared from the organ in question. Of course, peptones may also be prepared from bacilli, or else from certain proteins. The serum is mixed with the peptone solution and poured into a polarization tube, of a capacity of 2 c.c., and the angle of rotation of the mixture, at a temperature of
