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methylene blue and subsequently by perchloride of mercury. It will be as well to contrast the results obtained here in the case of Calf M with those obtained in the case of Calf K, which was injected with blood from Horse F, which had been treated by injections of mercury perchloride only.

Points of interest in the results of both cases.

(1) The temperature. In the case of Calf K there was a definite initial rise of temperature during the incubative period after injection with blood, but no such rise of temperature took place in the case of Calf M.

(2) The appearance of trypanosomes in the blood-Trypanosomes appeared in the blood of Calf K after injection with blood, and then rapidly disappeared from the blood stream, but did not appear in the blood of Calf M injected with serum.

(3) General condition. Both Calf K and Calf M fell off in condition during the first month after injection; but Calf K fell off more so than Calf M, and also took longer to regain condition.

(4) Both calves were alive and well in January last.

Dog S (see Charts 37a to 37e) was, on the 16th May, injected subcutaneously with 10 c.c. of blood serum from Horse D; subsequently the temperature showed several rises, but the blood never showed any trypanosomes; the dog finally wasted and died on the 11th September, 1907.

On Post Mortem.-Dog much emaciated, papular skin eruption, organs anæmic, liver jaundiced, spleen enlarged and contents semi-fluid.

Remarks. In that the injection of some of the same serum from Horse D into Horse I reproduced the disease with trypanosomes in the horse's blood, it stands to reason that the serum of Horse D was infective and contained trypano- somes, but that the virulence of the strain of trypanosomes was lowered towards the dog by the treatment of Horse D, first by methylene blue and then by per- chloride of mercury, for the trypanosomes failed to develop in the dog and died out. The dog wasted and died, however, and death must therefore have been due to some toxic material already in the blood injected, or formed subsequently in the dog.

Monkey B (see Chart 38a to 38e).-Was on the 10th May injected subcutaneously with 10 c.c. of blood serum from Horse D. The chart of this animal shows some rises of temperature during the first month after injection, and subsequently the tempera- ture ran a normal course, but the blood showed no trypanosomes throughout. On the 30th September the observations of temperature were discontinued. During all this time the monkey kept in good health and spirits, and was now just kept under general observation. On leaving Maifoni early in November this monkey was taken down with me to Yola with the object of subjecting him to natural infection in a fly belt, but he was carried off one night by a wild animal, which prevented the experiment being completed in that it could not be ascertained if any degree of immunity had been established in the monkey by the injection of the serum.

Remarks. From the previous cases injected with serum from Horse D we know that it was infective to the horse and must have contained trypanosomes, which, however, were lowered in vitality, so far as the calf and dog were concerned, and so also we find it to be the case with regard to the monkey. The monkey, moreover, survived, whereas the dog died.

Thus we see that Calf K, injected with blood from Horse F, and Monkey A, injected with blood from Horse C, survived; the former showing trypanosomes in his blood temporarily, whereas the monkey did not develop any trypanosomes in his blood; that Calf M and Monkey B, injected with blood serum from Horse D, never developed any trypanosomes in their blood and survived. It may be noted here that Horse D was treated first by methylene blue and then by perchloride of mercury, whereas Horses F and C by mercury only.

Summary of results attained from experiments conducted under Section III., as well as from observations made on some of the cases under Section II., together with conclusions based on them.

(i) Blood taken from a horse treated by mercury perchloride and microscopically free from trypanosomes (see remarks on Dog O and Dog K, page 58), also the blood taken from a calf treated by mercury perchloride and microscopically free from trypanosomes (see remarks on Dog P, page 61), when injected subcutaneously into dogs does not produce a typical attack of the disease in them with the appearance

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of trypanosomes in the blood, but the dogs in some cases showed occasional rises of temperature and others not so. All, however, wasted away and eventually died after a considerable period as compared to the duration of life in a dog (usually from three to six weeks) after natural infection or infection with trypanosomes from a horse or ox that had acquired the disease naturally. It may be that the blood of these animals, after treatment by mercury, contained either-

(i) Some other phase of trypanosome, or (ii) some toxic product elaborated by the trypanosomes or resulting from the trypanosomes, owing to the treatment by mercury, which gave rise to a chronic infective process, and proved fatal eventually.

(ii) (a)--Blood taken from a calf treated by perchloride of mercury, but still found to contain trypanosomes when injected subcutaneously into dogs (see remarks on Dog H, page 63, Dog M, page 64, Dogs T and W, pages 66 and 67) fails to produce a typical attack of the disease, for the trypanosomes do not develop in the dog, and the cases run a similar course of those injected with blood as described under paragraph (i) on page. 27. In such cases the trypanosomes, though inoculated, appear to die out or change their phase, but the dog dies eventually after a prolonged period from (a) some other phase of trypanosomes or (b) some toxic product existing in the blood injected and derived from the trypanosomes, which prove infective and fatal. In that the try- panosomes do not develop in the dog, it would seem that the effect of treatment by perchloride of mercury in the horse is to lower the viru- lence of the stain of trypanosomes for dogs.

(b) The same remarks apply to blood taken from horses that had been treated by mercury perchloride and injected into dogs when it contained try- panosomes (see remarks on Dogs Q and R, page 69).

(c) The same remarks apply also to blood serum taken from a horse (see Horse D, page 14) that had been treated by methylene blue first and then by perchloride of mercury and injected into the dog (see Dog S, page 70) when it still contained trypanosomes.

(d) With regard to such blood (as mentioned in paragraph (b)) and such serum (as mentioned in paragraph (c)), the result of subcutaneous injection into horses (see Horse H, page 24, and Horse I, page 69) was to reproduce the disease and trypanosomes in the blood of the horses inoculated, with a fatal termination in each case.

(e) The results of the subcutaneous injection of such blood (as mentioned in paragraph (b)) and of serum (as mentioned in paragraph (c)) into calves are interesting (see the remarks on Calf K, page 68, and on Calf M, page 69), and are as follows:-

(1) The temperature.

The injection of the blood gave rise to a definite initial rise of temperature during the incubative period, but the injection of the serum caused no such rise of temperature.

(2) The appearance of trypanosomes in the blood after inoculation.

injection of the blood gave rise to trypanosomes in the blood of the calf for a short period, after which they disappeared, whereas the injection of serum gave rise to no trypanosomes in the blood of the calf that was injected.

(3) General condition.

As a result of injection both of blood and of serum the calves fell off in condition during the first month, but the one injected with blood more so than the one with serum and also took longer to regain his normal condition and health.

(4) Final result.

In both cases the calves injected appeared to have quite recovered and were well in January last, the outlook being hopeful.

(f) The result of injecting such blood (as mentioned in paragraph (b)) and of serum (as mentioned in paragraph (c)) into monkeys (see Monkey A, page 69, and Monkey B, page 70). In both cases the injections gave rise to some rises of temperature, but no trypanosomes were repro- duced in the monkeys inoculated. There were no signs of general ill-health, and both animals survived.