July 10, 1885.] 



SCIENCE. 



35 



From numerous examinations of the Oder water be- 

 fore and after filtration, Hulwa concludes, that, with 

 the exception of occasional disturbances at times of 

 high water, the impurities of the river-water are so 

 far removed by the process of filtration as to furnish 

 a drinking-water almost above suspicion. In order 

 to remove the fine particles of clay which give to 

 the water, in times of flood, an opalescent appear- 

 ance which filtration will not remove, Hulwa recom- 

 mended treating the water, before filtration, with alum 

 in the proportion of from one to ten parts of alum 

 to a hundred thousand parts of water (by weight), 

 according to the degree of turbidity of the water. 

 This use of alum, which is becoming very common 

 on a smaller scale, has not been adopted at Breslau. 

 At the time of Hulwa' s examinations, the sewage of 

 Breslau all ran into the Oder opposite and below the 

 city, in anticipation of the completion of the sewage- 

 farms now in use. The study of the effect of this 

 discharge upon the stream is perhaps the most inter- 

 esting part of the document. Although the volume 

 of sewage is, on the average, only t4¥ of the volume of 

 river- water, and in times of flood only ^^y, the river 

 opposite and just below the city gives abundant evi- 

 dence of pollution, — pollution which becomes less 

 and less marked as the stream flows. Thirty-two 

 kilometres below the city neither chemical nor mi- 

 croscopical examination was able to show any evi- 

 dence that the water was not quite as suitable for 

 water-supply (after filtration) as the water from the 

 same stream above the city at the present pumping- 

 works. Hulwa is of the opinion that the natural 

 purifying agencies are quite suflacient to take care of 

 the amount of sewage which was then discharged 

 into the river, and that, a fortiori, the effluent from 

 the sewage-farms may be safely disposed of in that 

 way. He is careful, however, to admit the possi- 

 bility of overloading this or any other stream, and 

 of calling upon the natural agencies to do more than 

 they are capable of doing. He thus agrees with most 

 experts who have studied this matter, that the dis- 

 charge of sewage or other polluting matters into a 

 stream is not to be decided in all cases by an abso- 

 lute prohibition, but that the size of the stream, the 

 proportion of polluting matters, and other circum- 

 stances, must be taken into consideration. 



THE CONSUMPTIVE PERIOD. 



Hippocrates declared that consumption gathers 

 the greatest number of victims between the ages of 

 25 and 35 years, and the same observation holds true 

 to-day. 



As a first and natural deduction from this fact, the 

 opinion has obtained, that men are more susceptible 

 to consumption between 20 and .35, and that, passing 



Die schwindsuchUsterhlichkeit in den ddnischen stddten im 

 verhdltniss zu der lebenden bevolkenmg in den verschiedenen 

 altemklaHsen und geschlechtern. Von Dr. Julius Lehmann. 

 (Erganzungshefte zum Centralbl. allg. gesundh., 18 p., pi. 8". 

 Bonn, 1884.) 



Ueber den einfluaa des geschlectea und des lebensalters auf die 

 Hckwind.mchtsfsterblichkeit. Von Dr. Jacob Sohmitz. Bonn, 

 1884. 



this period, they gradually acquire an immunity from 

 the disease. 



A more careful study of the statistics, however, 

 reveals a fallacy in this reasoning. Hitherto it has 

 been the custom to reckon the mortality of each 

 period of life as a fraction of the entire mortality of 

 all ages. By this method it is shown merely that 

 during certain decades of life more individuals die of 

 phthisis than during other decades. This amounts, 

 however, simply to saying that within these periods 

 of life a greater number of people are living. The 

 total number of deaths from any disease, at any given 

 age, must be greater or less, according to the number 

 of people existing at that age; and a large proportion 

 of mankind are from 20 to 35 years old. In order, 

 therefore, to determine the individual risk of con- 

 sumption at any specified time of life, it is necessary 

 to know the whole number of persons living at that 

 age, and then compute the percentage of them who 

 die of consumption. 



Figuring in this manner, Wiirzburg estimated the 

 annual percentage of mortality from phthisis at dif- 

 ferent periods of life in Prussia, and he found the 

 following table for every 10,000 persons living at each 

 period : — 



Age. 



Men. 



Women. 



Age. 



Men. 



Women. 



0-1 



24.95 



21.92 



25-30 



40.04 



33.58 



1-2 



20.27 



20.55 



30-40 



44.25 



38.12 



2-3 



12.09 



12.94 



40-50 



57.10 



40.10 



3-5 



6.49 



7.18 



50-60 



82.38 



54.48 



5-10 



4.07 



5.26 



60-70 



112.25 



76.09 



10-15 



4.35 



7.38 



70-80 



75.23 



50.03 



15-20 



17.87 



18.87 



Over 80 



31.71 



21.01 



20-25 



34.77 



25.93 









From this table it is seen that a large phthisis mor- 

 tality prevails during the first year of life; thence 

 it descends to a minimum between 5 and 15 years of 

 age; from this point it increases with rapid strides, 

 until, between 60 and 70 years, it reaches the high 

 figures of 112.25 per every 10,000 living beings of 

 that age : in other words, these figures mean that a 

 man's liability to death by consumption increases 

 from puberty till 70 years of age. 



The companion column of the phthisis mortality 

 of women shows that they are more frequent victims 

 during childhood, but during the third decade and 

 thereafter their relative liability is diminished. 



These figures of Wiirzburg are confirmed in their 

 main features by the investigations of Lehmann in 

 Copenhagen, and of Schmitz in Bonn. Lehmann 

 also extended his query to the relative duration of 

 phthisis at different ages, and found that under 20 

 years of age more than 75% of phthisis patients die 

 within a year. This rapid progress of the disease 

 diminishes with increasing years until at least one- 

 half of the cases terminating after 55 years of age 

 present a record from three to many years' dura- 

 tion. It follows from this that a portion of the in- 

 creased phthisis mortality of advanced years is due 

 to cases which have lasted over from the earlier 

 decades. 



