196 | Major R. Ross and Dr. D. Thomson. Sleeping [Oct. 15, 
At this time Dr. Moore Alexander, pathologist to the hospital, suggested 
that we should try leucocytic extract. He thought that this extract might 
contain certain substances which would be deleterious to the trypanosomes, 
or which would neutralise their endotoxins. He was good enough to prepare 
it for us by injecting Mellin’s food into the pleural cavities of rabbits. The 
rabbits were then killed, and the accumulation of leucocytes taken from 
the pleural cavity, and extracted with sterile distilled water. 
To our surprise, the effect of an injection of this leucocytic extract was to 
produce a very great increase of leucocytes in the blood on the day following 
the injection. This was almost the invariable result. In our opinion, it 
seems to be a far more powerful promoter of leucocyte increase than yeast or 
nuclein. 
We tried to utilise this discovery in two ways :— 
(i) To help the natural leucocyte increase by injecting the extract just at 
the height of the trypanosome rise. We did this on May 19. Next day, as 
we have mentioned, the patient showed a remarkable Oem We 
were unable, however, to get such a happy result again. 
(11) By injecting the extract a day or two before the rise of parasites, we 
thought we might prevent that rise by causing an early increase in the 
leucocytes. 
On May 31 10 cc. of the extract were injected, producing next day 
an increase of leucocytes up to 20,000 per cubic millimetre of blood, but they 
diminished next day to 2,800 per cubic millimetre, and the increase of 
trypanosomes occurred all the same. 
Later, just before the patient’s death, we tried the effect of 1 c.c. doses of 
the extract daily. This seemed to keep the leucocyte count high, but unfor- 
tunately the results were complicated by the patient developing an abscess at 
this time, and later by the development of pleuropneumonia. 
Further investigation with this substance, and with vaccine, would require 
to be made before coming to any definite conclusions. Such an investigation 
we think would lead to further knowledge regarding the natural balance of 
immunity between the body and the parasites. 
It appears to be a law (at least it seems to hold good, we think) with 
leucocytes and trypanosomes, that the extract of dead animal cells stimulates 
the corresponding live cells to increase in numbers. This would appear to 
support the hypothesis put forward by Dr. H. C. Ross, that the extracts of 
dead tissues promote the proliferation of living cells.* 
* ‘Brit. Med. Journ.,’ June 11, 1910. 
