184 BACTERIA IN MILK AND MILK PRODUCTS 



the manipulation, there will always be a residue remaining in the 

 ducts, which will, and does, afford a suitable nidus and incubator for 

 organisms. The latter obtain their entrance through the imperfectly 

 closed teat of the udder, and pass readily into the milk-duct, some- 

 times even reaching the udder itself and setting up inflammation 

 {mastitis). Professor Eussell states that he has found 2800 germs 

 in the fore-milk, in a sample of which the average was only 330 per 

 c.c. Schultz found 83,000 micro-organisms per c.c. in the fore-milk, 

 and only 9000 in the mid-milk. As a matter of fact, most of this 

 large number belong to the lactic acid fermentation group, and the 

 fore-milk rarely contains more than two or three species, and still 

 more rarely any disease-producing bacteria. Still, bacteria occur in 

 such enormous numbers that their addition to the ordinary milk 

 very materially alters its quality. BoUey and Hall, of North Dakota, 

 report sixteen species of bacteria in the fore-milk, twelve of which 

 produced an acid reaction. Dr Veranus Moore, of the United States 

 Department of Agriculture,* concludes from a large mass of data 

 that freshly-drawn fore-milk contains a variable but generally 

 enormous number of bacteria, but only a few species, the last milk 

 containing, as compared with the fore-milk, very few inicro-organisms. 

 The bacteria which become localised in the milk-ducts, and which are 

 necessarily carried into the milk, are for the greater part acid- 

 producing organisms, i.e., they ferment milk-sugar, forming acids. 

 They do not produce gas. Nevertheless their presence renders it 

 necessary to " pasteurise " as soon as possible. Dr Moore holds that 

 much of the intestinal trouble occurring in infants fed with ordinarily 

 "pasteurised" milk arises from acids produced by these bacteria 

 between the drawing of the milk and the pasteurisation. Prof. 

 MacFadyean has given a full account of the ways in which milk 

 becomes pathogenic, and his views have received further support from 

 Prof. DeMpine.f 



The Number of Bacteria in Milk 



From all that has been said respecting the sources of pollution 

 and the favourable nidus which milk affords for bacteria, it is not 

 surprising that a very large number of germs are almost always 

 present in milk. The quantitative estimation of milk appears more 

 alarming than the qualitative. It is true some diseases are conveyed 

 by bacteria in milk, but on the whole most of the species are non- 

 pathogenic. Nor need the numbers, though serious, too greatly 

 alarm us, for, as we shall see at a later stage, disease is due to other 

 agencies and conditions than merely the bacteria, which may be the 



* Bureau of Animal Industry Reports, 1895-96. 

 f Jour. ofConvp. Path., 1897, v.ol. x., pp. 150-189. 



