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From the foregoing paragraphs (d) (e) and (f), we note that the blood from the horse treated by perchloride of mercury, and the blood serum of the horse treated first by methylene blue and then by perchloride of mercury, are both still infective, for they contain trypanosome, and that the virulence of the organisms was not lowered with regard to the horse, in that both Horses H and I died, but was lowered with regard to calves and monkeys, in that Calf K, which was inoculated with blood, developed a mild attack of the disease, with trypanosomes in the blood, and then recovered, whereas Calf M, which was inoculated with serum, developed milder clinical symptoms, with no trypanosomes in the blood, and then recovered. It is worth noting here that the result of injection of serum produced milder clinical results in calves than those due to the injection of blood, and moreover that the serum was obtained from a horse treated by a course of methylene blue followed by a course of perchloride of mercury, whereas the blood was obtained from a horse treated by perchloride of mercury alone. So also it is seen on page 62 that the effect of treatment both in horses and calves by a course of methylene blue followed by a course of perchloride of mercury gave better results than treatment by per- chloride of mercury alone.

(3) The inoculation of a dog with blood from a horse, which is microscopically free from trypanosomes as a result of treatment by mercury, (see Dog J, page 65, and Dog W, page 67), appears to possess a protective effect, for if subsequently blood from an animal which contains trypanosomes and which has not been treated by mercury be inoculated into the dog trypanosomes fail to develop in the blood of the dog; the trypanosomes evidently die out, but the dog finally succumbs to some form of infection, as described under paragraph (ii) (a), page 71.

(4) The inoculation of a dog (see Dog M, page 64) with blood from a calf that contains trypanosomes, after having been treated by a course of mercury, did not reproduce the disease, and when subsequently inoculated with blood from a calf suffering from trypanosomiasis, but had not received any treatment, the trypano- somes failed to develop in the dog, showing that the first inoculation seems to have had some protective effect.

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These two paragraphs, 3 and 4, point to inoculation of blood from animals treated by perchloride of mercury having a protective value, but this conclusion is modified by the results obtained in a subsequent case, as seen in paragraph 5.

(5) From the results obtained in Dog V, page 67, which was used as a control to Dog W. we see that virulent trypanosomes in the blood of Calf L, which had received no

which had treatment, failed to develop in Dog V, been protected in any way by inoculation, and it leads us to conclude that the only other factor which lowers the virulence of a strain of trypanosomes towards the dog is the constant maintenance of a strain of trypanosomes by inoculation and subinoculation through a series of animals. It may be, however, that some previous treatment by mercury of one of the animals through which the strain had passed may have had some share in lowering the virulence of the strain, and this may have been the case here, for Calf L was inoculated with trypanosomes from Calf J after Calf J had been treated by mercury for three days.

In short we see that the virulence of a strain of trypanosomes is lowered by two factors, viz.:-

(1) The effect of treatment by perchloride of meṛcury.

(2) The passing of the strain by subinoculations through a series of animals. The latter is well illustrated in the case of Dog V, page 67, the former in the cases of Calf K, Dog Q, Dog R, and Monkey A, which were injected with blood from a horse treated by perchloride of mercury only (see page 69), and in the cases of Calf M, Dog S, and Monkey B, which were injected with serum from a horse treated first by a course of methylene blue and then by perchloride of mercury (see pages 69 and 70).

The degree to which the virulence of the strain has been lowered by the above- mentioned factors:-

(a) Least so far as the dog goes, for all have ultimately died, although no

trypanosomes have developed in their blood.

(b) The lowering of virulence of the strain is most marked so far as calves and monkeys are concerned, and of these the results in calves is of the most practical value.

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Further Experiments to be Conducted.

Calves K and M are to be subjected to natural infection in a fly belt, or inocu- lated with trypanosome from an animal which has naturally acquired the disease; and at the same time two healthy calves will be subjected to similar infection as a control with a view to ascertaining if the animals have been rendered immune to any degree against fresh infection.

Recommendations.-That a further series of experiments be conducted on the subject of immunity, and that the blood of Horse D and Calf F, which have so far recovered after treatment, as well as the blood of Calf K. and Calf M, which have recovered after inoculation with attenuated trypanosomes, be utilised further in trying to immunise other horses and cattle.

The foregoing report practically embodies the results attained in experimental work on Animal Trypanosomiasis conducted Maifoni, South Bornu, for over 12 months, from September, 1907, to the end of October, 1908.

In conclusion I wish to say that I feel I cannot express my thanks sufficiently to Major McClintock, the Resident. of the Province, for all the help he gave me, which enabled me to conduct this experimental work.

H. ANDREW Foy, Medical Officer,

London,

15th August, 1909.

37665

No. 22.

West African Medical Staff.

MEMORANDUM BY DR. BAGSHAWE ON THE INTRODUCTION OF SLEEPING SICKNESS BY SEA.

Rules have been made at Calcutta and the ports of Ceylon to control, or prevent, the introduction of sleeping sickness by sea. Similar rules are suggested for ports on the West Coast of Africa. 1 propose, therefore, to consider the subject in some detail.

Three possible cases may be taken. The introduction of the disease:-

(1) To tropical countries where no species of tsetse exists.

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(2). To parts of tropical Africa or Arabia where there are species of tsetse but

no Glossina palpalis.

(3) To parts of tropical Africa where Glossina palpalis is found.

(1) The answer to the question whether there is danger in introducing cases of sleeping sickness to tropical countries outside Africa depends on the mode of convey- ance of the human trypanosome from the sick to the healthy. If it is proved that Trypanosoma gambiense can be transmitted by a tsetse fly only, the taking of pre- cautions in countries where there are no tsetse flies is unnecessary.

In the days of the slave trade many infected African natives were transported to other countries where they developed the well-known nervous symptoms and died. Cases are described by Guerin, in Martinique (1869), by Nicolas, in Guadeloupe (1872), by Gore, in the Bahamas (1865), and by Ribeiro, in Brazil (1871). In these countries there were biting insects which might have transmitted the disease, but there is no evidence that it spread, and it is quite certain that when the slave trade ceased the disease disappeared. Similarly in tropical Africa the recorded instances of the spread of the disease from sick to healthy in the absence of tsetse flies are very few, and some of these can be accounted for by the hypothesis that sexual coitus may be a rare mode of infection.

Recently the members of the French Sleeping Sickness Commission, which spent two years in French Congo, have stated their belief that while Glossina palpalis necessary for the establishment of an endemic focus of the disease mosquitoes and perhaps other biting insects are accountable for its epidemic occurrence in houses and villages. Their view cannot be lightly dismissed, as it is supported by many instances, but it is probable that there is a fallacy in their argument. The observa- tions were made by men who were travelling, and in districts where palpalis existed in larger or smaller numbers. Such a point cannot be satisfactorily established unless the observer remains for weeks or months at the suspected place, noting what biting insects are found and studying the habits of the natives. It may be thus shown that women and children supposed to have become infected by mosquitoes in their huts have actually visited tsetse-haunted streams, which in nearly all the cases have been near. Observers in other parts of tropical Africa do not record

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