742 A MANUAL OF BACTERIOLOGY 



the cow and the hands of the milker (who should wear a 

 special dress) should be wiped before milking, and all 

 vessels should be clean and sterilised by steam immediately 

 before use. The milk should be milked into a "small- 

 top " pail, cooled to, and maintained at, about 50 F., 

 the newer types of milk churn adopted, and the milk 

 riot stored, but forwarded without delay by the railway 

 companies in special refrigerator vans. Distribution in 

 bottles would be a great improvement. 



Bacteriological Milk Standards. Houston suggested the follow- 

 ing tentative standards : 



1. Sediment (i.e. chiefly dirt) by volume 



(a) Primary reading, determined by sedimentation for twenty- 



four hours in a special cylinder, not to exceed 100 parts 

 per million parts of milk ; 



(b) Secondary reading, determined by centrifuging the dirt 



obtained by (a), not to exceed 50 parts per million. 



2. Presence of B. Welchii (determined by culture). Permissible 

 in 10 c.c., but not in 1 c.c., of the milk. 



3. Presence of B. coli { determined by culture). Permissible in 

 001 c.c., but not in 0-001 c.c., of the milk. 



There is no reason why a clean milk containing not more than 

 10,000 organisms per cubic centimetre when it reaches the con- 

 sumer should not be produced by the simple measures detailed 

 above. 



(On the hygienic relations of milk, see Principles of Prevent ire 

 Medicine, chapter xi, Hewlett and Nankivell (Churchill, 1921).) 



Soured milk. Soured milk is used as an article of diet in 

 many parts of the world, e.g. Bulgaria. In these soured milks a 

 particular micro-organism or a variety of it, the B. bulgaricus or 

 " bacillus of Massol," is generally present in association with lactic 

 streptococci. It is a large, pleomorphic, Gram -positive, aerobic 

 bacillus, non-motile, non-sporing, growing best at about 40 (., 

 but only in milk or in culture media made with milk or whey. 

 It has been much employed for the preparation of a soured milk 

 which is of considerable service in the treatment of certain dis- 

 orders. 1 



1 See Hewlett and others, Brit. Med. Journ., 1910, vol. ii. (Bibliog.). 



