1910.| Sickness studied by Precise Hnwmerative Methods. 195 
premature rise tends to be less high than it probably should have been in the 
natural course of events. If, however, the vaccine be injected during the 
natural rise of the trypanosomes, it stimulates their reproduction, causing a 
very high and rapid rise, and the subsequent fall is also very sudden. 
We confirmed these surmises later. On May 17 an injection of 30,000,000 
dead trypanosomes was given, with the result that the following rise was 
completed on the sixth day. 
Another injection of 50,000,000 on May 30 was followed by a rise at the 
normal time. <A large dose of 100,000,000, injected on June 4, however, 
scarcely allowed the parasites any time to diminish, so that they completed 
their next rise on the fifth day, followed by a sudden fall. Thus it would 
seem that the normal period of seven days between the rises of parasites 
may be shortened to six, five, and even four days, by an injection of dead 
trypanosomes. | 
Doses of vaccine up to 100,000,000 seemed to cause no harm. On the 
contrary, during the period from the 7th to the 28th of April, when small 
doses were given, the temperature was more uniform, and more near to normal 
than it had ever been before or after. 
Again, from the 14th to the 19th of May, the patient was extremely ill, 
almost comatose, with a high temperature, and like to die. On May 17 he 
had vaccine (30,000,000), followed on May 19 by an injection of 10 ce. 
of leucocytic extract. The improvement on May 20 was remarkable, both 
mentally and physically. Of course, at that time he had atoxyl and nuclein 
to increase the leucocytes, hence it is almost impossible to tell which was 
the potent factor. Against atoxyl having caused this good result, we may 
point out that it had no such effect either before or since. 
As already stated, this marked improvement was coincident with a large 
increase of mononuclear leucocytes. We tried again to repeat this success 
_ by injecting vaccine (100,000,000 trypanosomes) on June 4, three days before 
the height of the parasitic rise, and leucocytic extract at the height of the 
rise, but the result was not so good (vide paper by Ross and J. G. Thomson*). 
(9) The Hffect of Subcutaneous Injections of Leucocytie Extract. 
Thinking that the fall in the number of leucocytes might be a factor 
in the rise of trypanosomes, we determined to keep up the numbers of 
leucocytes when they were falling. Consequently, we tried an injection of 
nuclein (25 min.), but this did not seem to cause much increase of leucocytes. 
Yeast, 15 grains daily (by mouth), was also tried. It seemed to cause 
some increase, but not marked. 
* Infra, pp. 227—234. 
