78 MICRO-ORGANISMS AND DISEASE [cHAt>. 



of sterile water by means of a thoroughly clean nail-brush. 

 In this way the whole or practically the whole of the par- 

 ticulate matter of the bulk of water that had been filtered 

 is distributed in the lo cc. of sterile water. By brushing 

 the surface some of the soft filter material is also brushed 

 off, but since the bulk of this easily settles down it is of 

 no material consequence. This distribution is used for 

 cultivation ; every cubic centimetre of it contains the amount 

 of the particulate matter of a definite bulk of the original 

 water. If, for instance, 1,200 cc. had been driven through 

 the filter, each i cc. would contain the particulate matter 

 of 120 cc. of the original water; if 2,000 cc, each cc. 

 of the distribution contains the particulate matter of 

 200 cc. of the original water. There is no difficulty in 

 subjecting to analysis if necessary the whole 10 cc. — i.e. 

 the whole particulate matter of the whole of the original 

 2,000 cc. of the water. 



The cultivations of the distribution are made after Pari- 

 etti's method in phenolated gelatine, or in phenolated broth, 

 or in both. Parietti first pointed out that by adding a solu- 

 tion of phenol to the broth or the nutrient gelatine previously 

 melted, these media while remaining favourable for the 

 growth and development of the bacillus coli and typhoid, 

 are not so well suited to that of the ordinary water bacteria, 

 some of the latter being either altogether suppressed while 

 others thrive only slowly, and therefore bacillus coli or 

 typhoid have in the meantime an opportunity to develop. 

 Of a 5 per cent, solution of absolute phenol o'l cc. (or 

 100 cmm. ) are added to 10 cc. of broth or gelatine; this 

 represents the phenolated gelatine or phenolated broth 

 respectively. The addition of hydrochloric acid, as 

 recommended by some, is according to my experience not 

 required. 



