No. 3. A fresh bottle obtained at a Chicago retail store in December, 1913.
Portions of 1 gm. each of these samples were mixed with 5 gm. fibrin, 100 mg. of sodium carbonate and 50 c.c. of water in flasks. A little toluene was added to each flask, which was then closed with a tuft of cotton and the mixtures were incubated at 40 degrees through twenty-four hours. At the end of that time there was no marked change in the quantity of the fibrin remaining in each flask, the larger part by far being undigested.
As a control I used the sample of an active commercial trypsin, of which I added 500 mg. to the same quantity of water, fibrin and sodium carbonate. This was digested in the same bath at the same time. The digestion was practically completed in less than ten minutes, only minute flakes of the fibrin remaining.
It is evident that the digestive power of the Lactopeptine must be extremely low, and only a small fraction of that exhibited by a commercially good trypsin.
In an experiment with the English sample carried out through nineteen hours as above, using 2 gm. of fibrin and 100 mg. of ferment, it was found by nitrogen tests on the filtrate that about 12.2 per cent. of the protein had been brought into solution, an amount which is practically without importance in a digestion of such duration.
To test the starch digestive power I have made a large number of experiments. In a series just completed I mixed 1 gm. portions of Samples 1 and 2 with water to make 100 c.c. volumes. Before making up to the final volumes 0.5 c.c. of normal sodium hydroxid was added to neutralize the slight acidity of the ferment as shown by phenolphthalein.
Of these mixtures 4, 6, 8 and 10 c.c. portions were mixed with 50 c.c. of 1 per cent. starch paste and incubated at 40 degrees to find the colorless end-point in the starch digestion, by the iodin test.
At the end of twenty-two hours the iodin reaction was as strong as at the beginning, indicating no appreciable starch digestion.
To the flasks in which no digestion had taken place under these conditions, 5 mg. of a pancreas ferment was added. This gave an almost immediate conversion to the colorless end-point. This ferment was a sample of Holadin which had been in the laboratory about a year. The 5 mg. completed the reaction to the colorless end-point in less than ten minutes.