July 5, 1888J 



NATURE 



235 



Micro-organisms in Water. 

 The micro-organisms present in water have long been studied 

 by direct observation with the microscope. Such ohserva- 

 tions can, however, only be made in the case of foul waters in 

 which bacterial life is very abundant, and even in such cases the 

 information gained by the microscope alone has but little value. 

 It is to the modern methods of cultivation, more especially those 

 in which solid media are employed, that our increased knowledge 

 concerning these primitive inhabitants of water is due. Trm s 

 the beautiful process of plate-cultivation introduced by Koch, 

 and to which more than to anything else the recent advances in 

 bacteriology are due, has been of the greatest service in the in- 

 vestigation of a number of questions bearing on the micro- 

 organisms in water. The method of plate-cultivation consists, 

 as is well known, in taking some of the liquid or other substance 

 under examination for micro-organisms and mixing it with melted 

 gelatine-peptone in a test-tube, the mixture being then poured 

 out on a horizontal plate of glass and allowed to congeal, the 

 plate being then preserved in a damp chamber at a suitable 

 temperature. In the course of a few days colonies make their 

 appearance in the gelatine film, and can be counted and further 

 studied as required. This process is of extremely wide applica- 

 tion, for by this means pure cultivations of the various organisms 

 in a mixture can be readily obtained. If a definite volume of 

 water be submitted to this method of plate-cultivation, the 

 resulting colonies on the plate clearly indicate both the number 

 and the character of the organisms present in it. 



From numerous investigations made by means of gela- 

 tine plate-cultivations, it appears that whilst surface waters, 

 such as rivers, contain an abundance of microbial life, waters, 

 which like those from springs and deep wells have undergone 

 filtration through porous strata, contain but very few micro- 

 organisms. Now since such underground waters have at some 

 time or other been surface waters, it is obvious that in passing 

 through the porous strata of the earth they have been deprived 

 of those microbes which they contained whilst at the surface. 

 This removal of micro-organisms from water 2 also takes place in 

 a very marked manner when it is submitted to some kinds of 

 artificial filtration, such as that through very finely divided coke 

 or charcoal, as well as in the filtration of water on the large scale 

 through sand. The process of filtration, however, which abso- 

 lutely removes microbes with the greatest degree of certainty is 

 that introduced by Pasteur, in which the water is forced through 

 porous porcelain. It is especially noticeable that the efficiency 

 exhibited by these various materials in removing micro- organisms 

 stands in no sort of relationship to their chemical activity, i.e. 

 power of removing organic matter from water. Thus the porous 

 porcelain produces practically no change whatever in the 

 chemical composition of the water, whilst it deprives it entirely of 

 micro-organisms. 



The relative abundance of bacterial life in surface water, in 

 deep well water, as well as in surface water after filtration 

 through sand on the large scale, is well illustrated by the following 

 results. • - •'. 



Thus the average number of micro-organisms obtained during 

 the past year from a cubic centimetre (about twenty drops) of the 

 raw water as abstracted from the Rivers Thames a id Lea by 

 the metropolitan water companies was 21,500 and 13,200 re- 

 spectively. The same water, however, after having undergone 

 storage and filtration contained on an average respectively 500 

 and 450 micro-organisms in I cubic centimetre. It is at once 

 apparent, therefore, what striking results can be obtained by 

 sand filtration as at present carried out, and there is no doubt 

 that with the introduction of fresh improvements and increased 

 care an even greater reduction will be effected. 



In deep well water obtained from the chalk, which has under- 

 gone no artificial filtration, we find the remarkably low nu nber 

 of eighteen as the average for the year. Thus the artificial filtra- 

 tion through sand is far surpassed by the exhaustive filtration 

 through vast thicknesses of porous strata. 



Another point which has been brought to light thr nigh investi- 

 gating the micro-organisms of water by means of the improved 

 methods which we now possess is that many of the microbes 

 found in natural waters are capable of the most abundant multi- 

 plication 3 in the absence of practically any organic matter 



1 Mittheilungen aus dent kaiscrlichen Gesuruiheitsamte, Bd. i., 1881. 



2 "The Removal of Micro- organis 11s from Water," Prjc. Roy. Soc. 

 No. 238, 1885. , „ 



3 " On the Multiplication of Micro-organisms, Proc. Roy. Soc, No. 245. 

 1886. "Ueber das Verhalten versc'iied. Bacterienarten 1m Tnnkwasser, 

 Meade Bolton, Zeitschrift fur Hygiene, Bd. i. Heft 1. 



whatever. Thus, if the deep well water referred to above is 

 preserved for several days thoroughly protected from contamina- 

 tion through the air, and is then examined for micro-organisms, 

 it will be found that these have undergone an enormous increase, 

 1 cubic centimetre containing many thousands instead of the 

 ten or twenty usually present in the water at the time of pumping. 

 It has been found, moreover, that some of the water-organisms 

 are even capable of such abundant multiplication in water which 

 has been several times redistilled, and which is, therefore, almost 

 absolutely pure. From what source such organisms obtain their 

 necessary nourishment under these circumstances has not yet 

 been determined. The following figures serve to illustrate the 

 extent to which multiplication of this kind may take place : — 



Nuihber of Micro-organisms obtained from I cubic centimetre 

 of water. 

 Day of Collection. Standing 1 day Standing 3 days 

 Sample of Vater from'l at 20° C. at 20 C. 



Kent Co. 's deep well > 7 ... 21 ... 495,000 



in chalk ) 



It is often urged that the bacteriological examination of water 

 is of little practical importance, inasmuch as the micro-organisms 

 found are not necessarily prejudicial to health, and that the 

 method of examination does not aim at the detection of harmful 

 forms. A little more mature consideration, however, will show 

 that the actual detection of harmful or pathogenic forms is a 

 matter of very little importance, and that if methods of water 

 purification are successful in removing micro-organisms in general, 

 and more especially those which find a suitable home in natural 

 waters, there can be no serious doubt that they will be equally 

 successful in removing ha'mful forms, which are not specially 

 adapted for life in water. Could it be, fur instance, reasonably 

 contested that a method of purification which is capable of 

 removing the Bacillus aquatilis from water, would be incapable 

 of disposing of the Bacillus anthracis when suspended in the 

 same medium ? The supposition is, on the face of it, absurd, 

 and not a particle of experimental evidence can be adduced in 

 its favour. It is, therefore only rational to conclude that those 

 methods of water purification, both natural and artificial, which 

 succeed in most reducing the total number of micro-organisms, 

 will also succeed in most reducing the number of harmful forms 

 should they be present. m . .. 



As a matter of fact, however, pathogenic forms can and have 

 been discovered in waters by the process of plate- cultivation ; 

 thus the " comma-bacillus," which is by many authorities re- 

 garded as the cause of Asiatic cholera, was found by Koch in 

 some tank-water in India, and the bacillus which with more or 

 less probability is identified with typhoid fever has by Chante- 

 messe and Widal been discovered in the drinking-water which 

 had been consumed by persons suffering from that disease. 



On the other hand, the examination of water for the number of 

 micro-organisms present can have no value if the multiplication 

 referred to above has taken place. Thus, if the number of 

 micro-organisms present in a water is to throw light on the 

 natural purification it has undergone, the sample for examination 

 must be taken as near as possible to the point where it issues 

 from the water-bearing stratum, and, in the case of artificially 

 purified water, as soon as possible after it has left the purifying 

 apparatus. _. 



Of much more importance than the discovery of pathogenic 

 organisms in particular waters is the problem of ascertaining the 

 fate of pathogenic forms, when these are introduced into waters 

 of different kinds. A considerable amount of work has been 

 done in this direction with a number of typical pathogenic forms, 

 and some very remarkable results have been obtained. Thus it 

 has been found that the bacilli of authrax do not survive many 

 hours on being introduced into ordinary drinking-water ; their 

 spores, however, are not in any way affected by such immersion, 

 and even in distilled water the latter retain their vitality for 

 practically an indefinite length of time. In polluted water, such 

 as sewage, on the other hand, not only do the bacilli not 

 succumb, but they undergo extensive multiplication. Similarly 

 Koch's "comma-bacillus" was found to flourish in sewage, 

 being still present in very large numbers after eleven months 

 residence in this medium. In deep-well and filtered Thames 

 water, on the other hand, although the " comma-bacilli were 

 1 "Die Vermehrung der Bacterien im Wasser " Wolffhugel und Riedel, 

 Arbeiten a. d. kaiserlichen Gesnndheitsamte. ''Ueber das Verhalten, 

 &c " Meade Bolton. "On the Multiplication of M.c.porgamsms, Proc. 

 I Roy Soc ; also " Recent Bacteriological Research in connection with 

 I Water Supply," Soc. Chem. Ini., vol. vi.No. 5. 



