ferment obtained in this manner can then be concentrated at 40° C. in shallow dishes, and if desired the ferment obtained as a scaly residue. So prepared, the pepsin is certainly quite pure, that is comparatively, and although it may contain some albumose, the latter must be very resistant to the action of the ferment; indeed, pepsin is in many respects an albumose-like body itself. [29] Zeitschr. f. Biol., Band 22, p. 428. In any event, the enzyme prepared in this manner shows decided proteid reactions, and contains nitrogen corresponding more or less closely to the recognized composition of an albumose. My own belief, therefore, is that these enzymes, both pepsin and trypsin, are proteid bodies closely related to the albumoses. They are soluble in water and more or less soluble in glycerin; at least glycerin will dissolve them from moist tissues, or from moist precipitates containing them. Langley,[30] however, states, and perhaps justly, that we have no positive proof that either ferments or zymogens are soluble in pure strong glycerin, and that if they are soluble, it is extremely slowly. In dilute glycerin, however, these ferments dissolve readily, as we very well know. Furthermore, they are practically non-diffusible, and, like many albumoses, are precipitated in part by saturation with sodium chloride and completely on saturation with ammonium sulphate. [30] Gamgee’s Physiological Chemistry of the Animal Body, vol. 2, p. 4. 1893. When dissolved in water and heated above 80° C., these enzymes are decomposed to such an extent that their proteolytic power is totally destroyed. The amount of coagulum produced by heat, however, is comparatively small, though variable with different preparations. Thus with trypsin, Kühne originally considered that boiling an aqueous solution of the ferment would give rise to about twenty per cent. of coagulated proteid and eighty per cent. of peptone-like matter. With the purer preparations now obtainable there is apparently less coagulable matter present, and Loew[31] has succeeded in preparing from the pancreas of the ox a sample of trypsin containing 52.75 per cent. of carbon and 16.55 per cent. of nitrogen, and yielding only a small coagulum by heat. Loew considered the ferment to be a true peptone, but in view of our present knowledge regarding the albumoses, I think we are justified in assuming it to be an albumose-like body rather than a true peptone. At the same time it may be well to again emphasize the fact that our only “means of determining the presence of an enzyme is that of ascertaining the change which it is able to bring about in other substances, and since the activity of the enzymes is extraordinarily great, a minute trace suffices to produce a marked effect. From this it follows that the purified enzymes which give distinct proteid reactions might merely consist of very small quantities of a true non-proteid enzyme, adherent to or mixed