74 REVIEW — TROPICAL MEDICINE, ETC. 



Filariasis— Personally I cannot say much about filariasis in the Sudan. The only filaria I have 



continued found in human blood in this country was F. jierstans, and that in a Ugandese at Tautikia. 

 In the only case of elephantiasis whose blood I examined at night I failed to find embryos. 

 Neither have I found them in the blood of monkeys (Cercopithfcuf:) . Elephantiasis does 

 occur, but is apparently not a common disease. Singer' records that in South-Western 

 Abyssinia elephantiasis occurs, but is rare. Ensor has recently reported filariasis to be 

 common in the southern Bahr-El-Ghazal Province of the Sudan. 



Giilex fatiijans is common all over the Northern Sudan and occurs also in large numbers 

 on the Upper White Nile, but in these southern territories Mansouia uniformis is more likely 

 to play tlie part of a filaria vector. A great deal of useful information could be obtained 

 by the systematic examination of bloods at night in the various hospitals. So far as I know 

 nothing has been done in this direction. It would entail hard work in such a trying 

 climate, but during the winter months the examinations could be made without very much 

 discomfort or fatigue. It would seem advisable, in the case of elephantiasis patients 

 brought in for operation, to enforce the use of a mosquito net at night, as where G. fatujans 

 or M. uniformis are present the disease might be transferred from the sick to the healthy. 



The question of infection with Filaria medinensis is considered under the heading 

 "Guinea Worm" (page 83^. 



Filters. An important practical paper of recent date is that by Bulloch, Craw and 

 Atkin- on the relative efficacy of the Doulton, Berkefeld and Browiilow filters. An 

 investigation such as they conducted was urgently required, for doubt had been thrown on 

 the efficacy of the Berkefeld filter, despite the statements of Woodhead and Cartwright 

 Wood. The later investigators conclude that — 



Of all the filters tested, the Doulton filters alone uniformly prevented the direct transmission of micro- 

 organisms ; the Berkefeld filters all permitted direct transmission, with one exception, and all the Slack and 

 Brownlow filters gave contaminated filtrates immediately. In the case of the Berkefeld filters and the Slack and 

 Brownlow filters the germs passed through within 15 minutes from the commencement of filtration, v/hereas seven 

 out of ten Doulton filters withheld the organisms and gave sterile filtrates for four days and in three cases for 

 longer periods. As these tests were made with a water pressure varying from zero to 32'5 lb. per square inch, 

 often in a few seconds, the above examination appears to us to be not only severe but also conclusive. 



Craw has a supplementary paper on the grain of filters and the growth of bacteria 

 through them, and brings out some interesting points. He finds that the size of pore is very 

 small in the Doulton filter, relatively greater in the Pasteur-Chamberland, very much 

 greater in the Berkefeld, and in the case of the Slack and Brownlow filter the pores are of 

 striking magnitude. These points are very well brought out in a series of photographs. 



He concludes that the grain of a filter is a very important, if not the most important, 

 factor in governing the growth of bacteria through the filter mass, and that in the filtration 

 of fluids containing colloidal substances, suspended matter or micro-organisms, the chemical 

 nature of the filter mass will be eliminated very rapidly as a factor in the efficiency of the 

 filter owing to the formation of a coating of foreign material, derived from the Huid, over the 

 chemically active surface. 



As regards water filtration on a large scale, much valuable information will be found in 

 Hazeu's work, 2 which is far too little known on the eastern side of the Atlantic. A short 

 resume of the subject, comparing the English sand filter with the American mechanical filter, 

 is given by Eobiuson.' As he points out, the latter, where a chemical precipitant is 

 employed, are specially applicable to very turbid and muddy waters. The efficiency of the 

 mechanical filters depends entirely on the use of coagulants, hence the value of a paper by 

 Whipple and Lougley' on the necessity of using basic and not neutral alum in mechanical 

 filtration. With neutral alum the bacterial efficiency was only 95-5 per cent., while with 

 basic alum 98-4 per cent, was obtained. As a result they contend that specifications for 

 filter alum should always require that there shall be a substantial excess of alumina, that is, 



' Singer, C. (January 16th, 1905), "Notes on Cases met with in South-Western Abyssinia in March, 1904." 

 Journal of Tropical Medicine, p. 17, Vol. VIII. 



"- Bulloch, W., Craw, J. A., and Atkin, E. G. (.January, 1908), "On the Relative Efficacy of the Doulton, 

 Berkefeld and Brownlow Filters." Journal of Hygiene, p. 63, Vol. VIII. 



= Hazen, Allen, " The Filtration of Public Water Supplies." New York, 1903. 



* Robinson, W. J. (September 15th, 1906), " Artificial Purification of Water Supplies." Brilish Medical 

 Journal, p. 623, Vol. II. 



* Whipple, G. C, and Longley, P. F. (February, 1906), " Experience with the Use of a Non-basic Alum in 

 Connection with Mechiioical Filtration." Journal of Infectious Diseases, Suppl., p. 166, Vol. III. 



