98 Journal of the Mitchell Society [^Decemher 



and liberated into the circulation of the host at the time of 

 segmentation of the parasite is undoubtedly hematin. It at 

 once appeared possible, therefore, that we might find in this 

 substance one of the hypothetical toxins operative in malaria. 

 The investigation of this question now embraces a series of 

 ninety observations upon the effect of the intravenous injection 

 of alkaline hematin, eighteen rabbits having been used for 

 test purposes. 



technique. 



Materials Used and Their Preparation. — The hematin used 

 was derived from three sources, rabbit blood, dog blood, and 

 ox blood, but in all cases it was prepared by the Schalfijew 

 process. The solutions for injection were made in 0.85 per 

 cent, salt solution containing 1.5 or 2 per cent, bicarbonate 

 of sodium. The strength of the hematin employed has varied 

 from 1.5 to 5 milligrams per cubic centimeter. The hematin 

 was added to the sterile solvent and heated to 100° C. for five 

 to ten minutes, and was then allowed to stand for twelve to 

 twenty-four hours, when it was again heated and, while still 

 hot, filtered into sterile flasks. The subsequent treatment of 

 these solutions has varied somewhat. Solutions prepared thus, 

 and again heated to 100° C. for five to ten minutes have appa- 

 rently remained sterile. In a few instances, however, the 

 filtered solution has been autoclaved to insure sterility. 



It has been found extremely difficult to prepare hematin 

 solutions of absolutely uniform character. With a given prep- 

 aration of hematin and with the same technique in the prepara- 

 tion of the solutions, two distinct types of solution may be 

 obtained : one, a perfectly clear, deeply colored solution that 

 even under the microscope shows very few particles of pigment 

 suspension, and on standing shows no precipitation in the 

 flask ; the other, a turbid solution that appears chocolate brown 

 in thin layers and under the microscope shows myriads of 

 pigmented particles and droplets floating in an only faintly 

 colored fluid. Much of -this pigment is precipitated on allow- 

 ing the solution to stand. This latter " colloidal " type of 

 solution or suspension, manifests all the optical properties of 



