54 THOMPSON YATES LABORATORIES REPORT 
examinations of the blood — the geographical distribution of this parasite is but little 
known. Until recently it was believed to be confined to Africa, Manson 1 stating 
that ' this parasite is very common in the blood of natives of large districts in 
West Africa. I have found it in natives from Old Calabar and from the basin of 
the Congo, both in the coast natives and in those from the interior. Daniells 
informs us that he has found it in a native of British Central Africa residing on the 
East side of Lake Nyassa. In many parts of the endemic districts it occurred in 
about half of the population. Professor Firket, of Liege, has confirmed this 
observation as regards the Congo district. Sometimes it occurs along with F. diurna 
and F. nocturna in the same individual. I have never found it in West Indian negros, 
nor in fact, in natives of any country except West Tropical Africa, and in the aborigines 
of Demerara. I have twice found it in Europeans who had resided in the Congo.' 
Ozzard 2 and Daniells' found many cases of F. perstans among the 
aboriginal Indians ot Demerara — some 130 miles up the Demerara River, and also 
up the Berbice River. Daniells also discovered the adult forms of the worms 
among the aborigines of British Guiana. 
Observations on the Distribution of the Blood Embryos among 
West African Natives 
We had opportunities, during the sojourn of the expedition in Nigeria, of 
examining the blood of natives from all parts of the West Coast of Africa, from 
Sierra Leone at its Western extremity, as far as the Old Calabar district at the 
Eastern, and from the coast inland as far as the region of the kingdom of Sokoto 
some 500 miles in the northern direction, and as far as Yola on the Benue river 
easterly. Throughout the whole of this vast area, the natives appear to be infected 
with F. nocturna, diurna and perstans : and there can be no doubt that the distribution 
of these parasites will prove to be much more extensive in Africa, and probably 
throughout the tropical world, than is at present supposed. The native Kroo boys 
whom we examined both day and night, generally remain in a certain place for a 
period varying from a few months to a number of years, usually having left their 
native districts after reaching manhood, returning thither at intervals. As a large 
number of the others examined were prisoners, these had often remained the greater 
part of their lives in their own countries, and had been transported to the 
towns at which we met them, for confinement for political, criminal, and other offences. 
From our notes of cases we have made the following table, illustrating the 
number of cases of pure and mixed infection throughout the district mentioned above. 
In the table, N.D. and P. represent F. nocturna, diurna, and perstans respectively ; 
N.D., N.P., D.P., represent a double infection with F. nocturna and diurna, nocturna 
1. Manson, Tropical Diseases. London, 1900. P. 536. 
2. Ozzard, British Guiana Medical Annual, 1897. 
3. Danieils, British Guiana Medical Annual, 1898. 
