May 3, 1920.] 



Agricultural Gazette of N .S.W . 



335 



much better by being thoroughly filtered — for example, through cotton wool 

 or felt pads. Filtering is especially necessary where, as in the present case, 

 the watercourse is accessible to stock which wade in it when drinking, and 

 open for surface infections lying about the surrounding watershed tc) Ije 

 washed into it by rains. ,^ 



Table II. — Showing Numbers and Kinds of Micro-oro:anisms found in 



Sample Bl — Cream before Pasteurising. — The sample for plating was 

 collected from the bulk in the cream-receiving vat by means of a sterile pipette. 

 Each can of this cream had been graded choicest quality, then thoroughly 

 mixed in the cream-receiving vat f)f 300 gallons ca^^acity. The acidity wa.s 

 determined at 0-4i per cent, lactic acid. From the plates it is shown that 1 c.c. 

 of cream contained 108,35-5,000 micro-organisms, in which Bact. lactis acidi, 

 a desirable type, was the predominant organism. There were also present 

 30,000 peptonising bacteria including varieties of micrococci, sarcina, clada- 

 thvix and Bact. Jlnorescensliquefaciens, and 1,312,000 organisms of the coli 

 group or undesirable lactose fermenters. Their presence in such large 

 numbers is undoubted evidence of heavy pollution by fa?cal contamination. 

 Among the acid and acid coagulating bacteria were 7,000,000 streptococci, 

 the cells being oval and in long chains. Although these organisms coagulate 

 milk, on account of their resembknce to a pathogenic variety they are 

 regarded as undesirable. There were 6,000 chromogenic micrococci which 

 made litmus milk alkaline but were unable to liquefy gelatin ; these may 

 be classed as inert. -Some 5,000 colonies of yeast were counted, while the 

 2,000 mould growths were Penicillium sp. 



Sample B'2 — Cream immediately after Pasteurising. — The sample for 

 plating was collected by means of a sterile pipette immediately after being- 

 discharged from the outlet pipe of the pasteuriser. The cream had been 

 neutralised to 0-24 per cent, acidity with lime and pasteuri.sed by means of 

 the flash system, where a temperature of 182 degrees Fah. was reached for a 

 few seconds ; then cooled to 54 degrees Fah. by passing over pipe-coolers. 

 It will be seen from the figures in Table II that 108,355,000 micro-organisms 

 in 1 c.c. of the cream were reduced by pasteurisation to 14,480; of these 

 none were able to liquefy gelatin. Litmus milk was slowly made acid and 



