318 APPLIED BACTEEIOLOGY 



considered insufficient for the prevention of infectious 

 disease. There is an extremely large body of evidence 

 to justify the conclusion that the resistance offered by 

 the Pasteur-Chamberland tube is sufficient to prevent the 

 passage of disease organisms from natural water. This 

 evidence has been collected mainly in all parts of the 

 French possessions, and published by the French Govern- 

 ment ; and since the filters have been introduced into this 

 country and India, similar evidence has arisen. There 

 is, however, no evidence to show that the resistance 

 which it offers exceeds that which is necessary for afford- 

 ing trustworthy protection against water-borne disease. 

 It is, therefore, not possible to accept any filter of less 

 efficiency as affording a trustworthy guarantee against 

 infection. In experiments of this kind, care should be 

 taken to procure several specimens of the filter under 

 examination, and to ascertain that they fairly represent 

 those intended for ordinary use. It is also desirable, when 

 special test-organisms are artificially introduced, to avoid 

 the simultaneous introduction of small quantities of culture 

 material. 



It has been found that water and other fluids sterilised 

 by heat may retain a toxic capacity, setting up, for instance, 

 suppuration on inoculation into suitable animals ; while 

 the same liquid sterilised by filtration through a Pasteur- 

 Chamberland tube produced no effect. At the present 

 time these phenomena and the conditions which determine 

 them are not sufficiently worked out to make it possible for 

 filters to be adequately examined as to their capacity to 

 produce similar results. 



A very full and interesting report by Drs. Woodhead 

 and Cartwright Wood upon the efficiency of the various 

 types of filters in use will be found in the Bi-itish Medical 

 Journal, vol. ii., 1894, pp. 1053, 1118, 1182, 1375, 1486. 



