1886.] 



MICROSCOPICAL JOUENAL. 



63 



which produce disorders of the diges- 

 tive processes by setting up fermenta- 

 tions. These fermentations, in turn, 

 develop gases and products of an irri- 

 tating character which may cause 

 local catarrhs, or be absorbed into 

 the blood, and produce symptoms of 

 poisoning. This class of bacteria is 

 as yet hypothetical, so far as our 

 knowledge of special forms is con- 

 cerned, yet it should merit the atten- 

 tion of students of hygiene, and de- 

 serves careful investigation. 



How we shall test the disturbing 

 action of bacteria found in drinking 

 water is another difficult question. 

 The usual experimental animals, such 

 asrabbits, mice, guinea-pigs, pigeons, 

 etc., show different powers of reac- 

 tion to certain disease germs, not only 

 \vith reference to man, but also among 

 themselves. Gaft'ky* found none ot 

 these animals susceptible to the mi- 

 crobe of typhoid fever both when 

 inti'oduced subcutaneously or with the 

 food. Consequently this germ can 

 only be determined by its mode of 

 growth in various culture media and 

 its microscopic characters. This is 

 vii'tually true of the cholera-bacillus 

 also, since it requires in guinea-pigs 

 the use of caustic potash and opium 

 t(j make the animal organism a favor- 

 able medium for the multiplication 

 of this germ. 



The biological examination of water 

 to-day is therefore merely quantita- 

 tive, but it covers a ground very im- 

 perfectly covered heretofore by chem- 

 ical analysis. The fact that micro- 

 organisms can be removed from water 

 by filtration points out to us the direc- 

 tion in which this method of analvsis 

 can be made useful . We must keep the 

 sources of our drinking water as pure 

 as possible in the first place, and sub- 

 ject it to careful filtration before use. 

 This will set aside the hunting for 

 disease germs when the damage has 

 been done and will give us the com- 

 forting assurance that the onlv real 



* Mittheilungen a. d. Kais. Gesundheitsamt, Berlin, 



,39;- 



elements of danger have been almost 

 entirely removed. 



The effect of filtration on the chemi- 

 cal and biological ingredients of drink- 

 ing ^vater, and the efficiency of the 

 filters employed, has been carefully 

 noted from day to da}' for more than 

 a year past at Berlin. The following 

 table* gives the monthlv average of 

 bacteria in one cubic centimeter of 

 drinking water before and after filtra- 

 tion : — 



July, 

 Aug. 

 Sept 

 Oct. 

 Nov. 

 Dec. 



Jnn. 



Feb. 

 Mar 



River water — 1 

 before filtra- | 

 tion. 



After 

 filtration. 



1064 

 1440 

 2496 

 3251 

 466 

 811 



1843 



265 

 277 



63 

 21 

 27 

 57 

 39 



In one of 

 the city 

 houses. 



409 



157 

 114 



50 

 26 

 34 

 29 



Potomac water, as is but too well 

 known, becomes exceedingly turbid 

 after prolonged rains or storms. The 

 suspended matter, chiefly inorganic, 

 slowly subsides after a time, leaving 

 the water comparatively clear. 

 Efforts arc now being made to obtain 

 an appropriation for the purpose of 

 subjecting the water to thorough 

 filtration. This is certainly very 

 desirable when we consider the 

 amount of earthy matter which the 

 water holds in suspension after every 

 seN'ere rain, not to speak of the 

 large increase in bacteria at this 

 time, pointing to a large accession of 

 organic matter. The table below 

 gives the number of bacteria in one 

 cubic centimeter of water and shows 

 how the number of bacteria rises 

 and falls with the turbidity. Each 

 determination is the average of two 

 closely agreeing independent plate 

 cultures of the same specimen of 

 water taken from a constantly flowing 

 faucet in the basement of the Agri- 

 cultural Building. 



* Arbeiten a. d. Kais. Gc-sundheitsamt, KexUi?.. i, 7. 



