212 REPORT OF THE HARVARD AFRICAN EXPEDITION 
marked evidences of the ravages of malaria in any of the villages we visited, 
similar to what is sometimes seen in some South American towns, nor was the 
prevalence of mosquitoes as great in Liberia. 
It is interesting to compare the high rate of infection with malaria in Mon- 
rovia (in children, 86 per cent), with that observed by MacDonald? in the 
adjacent country at Freetown, Sierra Leone. He found splenic indices of 50 per 
cent in an endemic and 72 per cent in a hyperendemic area, while the parasitic 
rates were 41 per cent and 72 per cent. Of 49 boys examined up to seven times, 
98 per cent showed malarial parasites. In Senegal, at Dakar, Leger and Nogue ” 
found the endemic index in adults with parasites in the blood in the wet ma- 
larial season in Dakar to be 47.5 per cent, and in children under two years, 64 
per cent. Durieux and Sall* also found that the rate of infection in children di- 
minished with the age, a percentage of infection of 50 in children of less than 
five years of age diminished to 34.3 in those of five to ten years and to 20.5 in 
those of ten to fifteen years. Under prophylactic measures the index for malaria 
in some localities was reduced from 50 to 24 per cent. Barreto,* in the study 
of endemic indexes of malaria in Portuguese Guinea, found that of 236 natives, 
32 per cent were parasitized with the haematozoa of Laveran. The plasmodial 
index at Baloma was 57 per cent and at Buba 42 per cent. The splenic index, 
however, was always below this amount. The rate of infection with the para- 
sites was found to vary greatly with the season of the year. 
Ledentu and Vaucel® found, near Brazzaville, in the examination in seven 
villages, of 153 children, less than five years of age, that 36 per cent of them were 
infected with malarial parasites. The splenic index was higher in the younger 
children. The parasitic index, however, was always greater than the splenic 
index. Of 283 natives that were infected with malarial parasites, in 63 the 
spleen was enlarged (22.2 per cent), but in 220 the spleen was not enlarged 
(77.8 per cent). In the examination of 891 natives who had no parasites in their 
blood, the spleen was enlarged in 113 or 12.6 per cent. They found that the 
enlargement of the spleen was more common in Plasmodium vivax infections. 
Of these 645 had a large spleen and 1438 no enlargement. 
In our medical survey made of the Bassas, Grebos, and Kpwesi tribes, in 
which 33.33 per cent were found to be infected with malarial parasites and 
sixteen per cent with enlargement of the spleen, here again no case of very pro- 
nounced splenomegaly was encountered among them. 
Almost no one doubts the value of the splenic index as affording a simple and 
rapid method of estimating the degree of malaria in some infected areas, but on 
the other hand it certainly does not furnish a means of discovery of all malarial 
infections, and it would be exceedingly unwise in certain tropical districts to 
assume that all cases of splenomegaly are necessarily malarial in origin. 
Dr. Shattuck, on the present Expedition, concluded from his clinical studies 
1 MacDonald: Ann. Trop. Med. and Parasit. (1926), XX, 239, 
2 Leger and Nogue: Bull. Soc. Path. Exot. (1923), XVI, 281. 
§ Durieux and Sall: Bull. Soc. Path. Exot. (1929), XXII, 618. 
Barreto: Bull. Soc. Path. Exot. (1927), XX, 280. 
Ledentu and Vaucel: Bull. Soc. Path. Exot. (1927), XX, 722. 
