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THURSDAY, SEPTEMBER 7, 1893. 



THE PUBLIC HEALTH LABORATORY. 

 Public Health Laboratory Work. By Henry R. Kenwoodj 

 M.B., D.P.H., F.C.S., including Methods employed in 

 Bacteriological Research, with Special Reference to the 

 Examination of Air, Water, and Food, contributed by 

 Robert Boyce, M.B. Crown 8vo. 491 pages. (London : 

 H. K. Lewis, 1893.) 



AN organised laboratory for the practical instruction 

 of students of hygiene is a comparatively novel 

 creation, the demand for which has principally arisen 

 in connection with the various diplomas in Public Health 

 (D.P.H.), which are now eagerly sought after by those of 

 the younger generation of medical men who contemplate 

 the possibility of becoming at some future time candi- 

 dates for appointments as medical officers of health. 

 Probably there are many persons who, whilst having a 

 general acquaintance with the studies which are pursued 

 in ordinary scientific institutions, are yet altogether 

 ignorant of what is being done in these public health 

 laboratories, which have grown up within recent years. A 

 glance at the table of contents in the work before us will 

 [ at once reveal what a wide and varied field this subject of 

 '. public health is made to cover, including as it does the 

 I hygienic analysis of air and water, the examination of 

 I food (milk, butter, cheese, corn, bread, meat, alcoholic 

 beverages, mustard, pepper, sugar, coffee, chocolate, tea, 

 and tinned provisions), together with the "methods em- 

 ployed in bacteriological research, with special reference 

 ^ to the examination of air, water, and food." That this is 

 \ a very comprehensive programme will be admitted by all, 

 i whilst it is equally patent to the initiated that it is one 

 ! which it must be extremely difficult for a single teacher 

 ' to conscientiously undertake, involving, as it does, an 

 I adequate knowledge of the most miscellaneous subjects. 

 Inasmuch, however, as the ground covered is mainly of a 

 i chemical nature, it is obvious that the methods of work 

 'prescribed must be such as shall recommend themselves 

 to chemists. In this connection it is interesting to note 

 I that the student is supposed to present himself at the 

 public health laboratory without any previous know- 

 1 ledge of practical chemistry, at any rate as far as quan- 

 ititative methods are concerned. Thus he has even to be 

 initiated into the mysteries of such simple contrivances 

 a? the Bunsen burner, the pipe-clay triangle, and even the 

 I homely pestle and mortar, articles with which we 

 '.should have supposed that most Board School children 

 of the higher standards were now acquainted. 



The first and largest section of the book is devoted to 

 |the subject of water analysis, the practice of which 

 .appears to form the point de resistance of the hygienic 

 (laboratory. For the information of those who have not 

 ^had the benefit of receiving their instruction in such a 

 {laboratory we will cite a few examples of the practical 

 (methods which appear to be in vogue there. Chemists 

 will be interested to learn that in using the balance the 

 'weights should be adjusted until " the index rests abso- 

 lutely in a central and vertical position ! " In determining 

 jthe total solid matters in water, the only drying of the 

 residue obtained by evaporation which is advocated is 

 NO. 1245, VOL. 48] 



to place the dish containing it "for a few minutes in tl.e 

 water-oven," and even this appears to be regarded as «n 

 almost excessive refinement, for we are also informed that 

 "when recourse is not had to the water-oven, the undei- 

 surface of the dish must be always carefully wiped diy 

 before the dish and its contents are weighed." Such in- 

 structions might have been allowed to pass had sume 

 apology been made for the necessarily crude work alone 

 to be expected from public health students, but when a 

 little further on we are informed that the time involved 

 in the evaporation of 100 c.c. of water is liable to introduce 

 error through loss of organic matter in the water, anti 

 through the access of suspended matter from the air, it 

 is obvious that the writer is under a wholly false impres- 

 sion as to the degree of accuracy obtainable by the 

 methods he describes. 



For the estimation of organic matter in water, the 

 author has recourse principally to the so-called "al- 

 buminoid ammonia" process, but since the adaptation of 

 the Kjeldahl method to water-analysis by Drown, there is 

 now no reason why even in a poorly equipped laboratory 

 an accurate determination of the total organic nitrogen 

 should not be made, in addition to that of the variable 

 fraction of this ingredient which makes its appearance 

 on distilling the water with alkaline permanganate. The 

 author describes the combustion process for organic 

 carbon and nitrogen, but as something entirely beyond 

 the sphere of the public health laboratory. The de- 

 scription given of this process would not appear to be 

 derived from personal experience, whilst the suggestion 

 that carbonic oxide is produced in the combustion, and 

 volumetrically measured in the subsequent gas analysis, 

 indicates but a very imperfect notion of what a satisfac- 

 tory combustion with oxide of copper should accomplish. 



We hardly think that the author has been successful in 

 giving a lucid exposition of the important and much-vexed 

 question of the activity of water on lead, for the statement 

 that this activity " is favoured by either neutrality or slight 

 alkalinity of the water (acidity, however, is even more 

 important, since it aids the power of the water to carry 

 the lead in solution) " is surely a somewhat circuitous way 

 of saying that the lead-dissolving power of many waters 

 is still wrapped in much obscurity. 



Again, in the description of the preparation of normal 

 solutions for volumetric analysis we read : " The number 

 of grammes of the reagent are weighed out and dissolved 

 in a litre of water," an inaccuracy which is repeated on 

 the same page in the statement that a normal solution of 

 hydrochloric acid is one consisting of " 36'37 grms. of 

 hydrochloric acid to a litre of distilled water." 



In the chapter on coal-gas we are surprised to hear 

 that the average gas supplied by the London companies 

 contains 3 per cent, of carbonic acid : in all the pub- 

 lished analyses of London coal-gas, and there are many, 

 although the analysis only of Heidelberg gas (!) is re- 

 corded in the work before us, carbonic acid is either 

 absent altogether or only present in small traces, for 

 the gas managers are well aware that 3 per cent, of this 

 ingredient, so prejudicial to the illuminating power, would 

 entail great expense in bringing the luminosity of the 

 gas up to the parliamentary standard. 



Notwithstanding some shortcomings of this kind, the 



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