434 BACTERIOLOGICAL ANALYSES 



21. Determine the pathogenicity for mice (subcuta- 

 neous inoculation) and rabbits ( intravenous inocula- 

 tion) of the streptococci isolated. 



On the facing insert page is reproduced a blank from 

 the author's Laboratory Water Analysis Book, by 

 means of which an exact record can be kept, with a 

 minimum of labour, of every sample examined. 



B. Concentration Method. 



The remaining organisms referred to on page 426 

 are more conveniently sought for by the concentration 

 method. 



Collection of the Sample. The quantity of water 

 required for this method of examination is about 2000 

 c.c., and the vessel usually chosen for its Vecep "^n is 

 an ordinary blue glass Winchester quart bottle, ster- 

 ilised in the hot-air oven, and over this a paper or parch- 

 ment cap fastened with string. The bottle may be 

 packed in a wooden box or in an ordinary wicker case. 

 The method of collecting the sample is identical with 

 that described under the heading of Quantitative 

 Examination; there is, however, not the same impera- 

 tive necessity to pack the sample in ice for transmission 

 to the laboratory. 



Apparatus required: 



Sterile Chamberland or Doulton " white " porcelain open mouth 

 filter candle, fitted with rubber washer. 



Rubber cork to fit mouth of the filter candle, perforated with 

 one hole. 



Kitasato serum flask, 2500 c.c. capacity. 



Geryk air pump or water force pump. 



Wulff's bottle, fitted as wash-bottle, and containing sulphuric 

 acid (to act as a safety valve between filter and pump). 



Pressure tubing, clamps, pinch-cock. 



Retort stand, with ring and clamp. 



Rubber cork for the neck of Winchester quart, perforated with 

 two holes and fitted with one 6 cm. length of straight glass tubing, 

 and one V -shaped piece of glass tubing, one arm 3 2 cm. in length, 

 the other 52 cm., the si orter arm being plugged with cotton- wool. 

 The rubber stopper must be sterilised by boiling and the glass 

 tubing by hot air, before use. 



