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deal with unemployment among young persons(Part X). Its perusal will quicken the interest andsympathy of those already familiar with the specialareas, and should stimulate others to an awarenessof the position.

LONDON WATER

THE Metropolitan Water -Board has many notableachievements to its credit. Not the least is thewisdom it has shown in selecting directors of waterexamination who can write. Houston always hadsomething to say, and said it, and Lieut.-ColonelC. H. H. Harold is a worthy successor. In this

respect and in the absence of acrimony and specialpleading, the whole series of annual reports differs

greatly from those of the three eminent chemistsretained by the eight water companies whose under-takings were taken over thirty years ago. The taskwhich the Board has set itself-to supply one

standard of water only, coliform organisms absent in100 ml.-is no easy one. That may be easy enoughfor undertakings drawing their raw water from

upland sources well away from and for the most partabove human habitations, but when the sources arerivers passing through large and populous towns,and wells in districts which are suburban ratherthan rural, it is only by unremitting watchfulnessthat such an aim can be reached.The work of the Board’s laboratories i is divided

into three sections-bacteriological, biological (orplanktonic), and chemical. In the bacteriologicalsection an experiment into the possible multiplicationof B. coli aerogenes and other organisms in cisternsand filter beds was conducted.

It was found that filtered Thames water, initially con-taining no coliform organisms in 100 ml. and giving anagar count of 30 colonies per ml., kept in a plugged andcovered bottle, yielded a considerable increase of sapro-phytes in 24 hours, which gradually disappeared after5 to 6 weeks, but no aerogenes. The same water inocu-lated with either aerogenes, communior, griinthal or

communis (from 270 to 410 per ml.) yielded no aerogenesor communis in 2 weeks, and no communior or grunthalin 3 weeks. Treated with ozone and similarly inoculated,the aerogenes and griinthal disappeared in 2 and the othersin 3 weeks. In these samples as in the control sapro-phytes appeared, and after a few weeks disappeared.When sterilised with chlorine so that no residual sterilantwas present after 24 hours, saprophytes did not appear,and communior disappeared in 3 weeks, but aerogenespersisted for 10 weeks and grunthal and communis for7 weeks. The same water boiled yielded no saprophytes,but aerogenes increased from 270 to 40,000 in 5 weeksand disappeared in 27 weeks, whilst the other organismswere not found after 5 or 6 weeks. The water againbecame negative to MacConkey in from 2 to 30 weeks, thebest times being given by the ozonised group.It would appear, Colonel Harold remarks, that theviability of coliform organisms is influenced largelyby the presence and multiplication of saprophyticsurvivors, and the extent to which these prevaildepends largely upon the efficacy of the initial processof disinfection employed, although there may beother contributory factors.The biological section of the report is of great

interest, and it appears that Colonel Harold intendsto develop a branch of water examination which hasbeen somewhat neglected in this country, althoughHouston and Mr. Wilfred Rushton, D.Sc., amongothers, have done useful work. Fresh-water planktonhas been studied more intensively in the United

1 Metropolitan Water Board: thirtieth annual report. ByLieut.-Col. C, H. H. Harold, M.D., D.P.H., director of waterexamination. London: P. S. King and Son, Ltd. Pp. 101.10s. 6d.

States and Central Europe than in most othercountries. Colonel Harold gives photographs of aplankton net and sampling bottle regularly used on amotor launch on the Queen Mary Reservoir. Forreasons which are not clear, lakes and reservoirs arericher than rivers in both phyto- and zoo-plankton.The fact that there are few lakes of any size in thiscountry and that these are relatively far from seatsof learning may account for the slow development ofecological as distinguished from morphologicalstudies of fresh-water plankton in Great Britain.The Freshwater Biological Association of the BritishEmpire in February, 1932, opened a laboratory atWray Castle on Windermere for the study of thatlake. On the balance of these two classes dependsthe probability of trouble arising from unusual tastesand smells or from the blockage of filter-beds. The

vegetable plankton develops from spores by photo-synthesis, the carbon dioxide of bicarbonates supply-ing what carbon is required, whilst nitrogen andmineral constituents are obtained from nitrates andother salts dissolved in the water. As the algalflora develops pasturage becomes available for theanimal population. Increase of both kinds of

plankton can go on until the least plentiful plantfoods are exhausted in the water; these seem to besilicates, phosphates, and oxidised nitrogen (nitratesand nitrites). The development of the phyto-plankton is also dependent on the effective penetra-tion of the water by sunlight; hence a rather com-plicated seasonal variation occurs.The study of plankton seems already to be enabling

its control by algicides, such as copper sulphate aloneor combined with chloramine, to be put on a sounderbasis, and should do much to remove the troubles towhich Houston so often referred. The chemicalsection, too, is devoting attention to the determina-tion of those minute amounts of constituents whichare limiting factors in the growth of plankton.

CAUSES OF STERILITY

AMERICAN medicine, with its capacity for organisa-tion, has gone further than the rest of us in thetreatment of the childless marriage, and a symposiumappearing in the Journal of the American MedicalAssociation for Dec. 5th is valuable as reflectingpresent opinion in the United States. The firstcontribution is by S. R. Meaker, who has done moreperhaps than any other physician to call attentionto the need for really careful investigation of bothhusband and wife if children are wanted and havefailed to appear. In at least 70 per cent. of cases ofhuman sterility the cause is not some single abnor-mality but rather the summation of several factors.Some of these may be genital and some may beconstitutional; and they are seldom limited to onepartner. Meaker and his associates state that onlyabout 10 per cent. of the husbands and 5 per cent.of the wives that consult them for childlessness arefree from all objectively demonstrable evidence ofinfertility. In women the four most importantgynaecological abnormalities are genital hypoplasia,abnormal viscosity of the endocervical secretions,partial or complete obstruction of the Fallopiantubes, and faulty ovulation. The most difficult ofthese to detect is the last ; for no method of examina-tion has been devised that will show whether or notthe ovaries actually liberate mature and normaleggs. In treatment Meaker would have us correctevery factor demonstrated as inimical to fertility.A therapeutic approach from several directions givesresults far better than those obtained in older days