BACTERIA IN FOODS 1 89 



qualitative one. The kinds commonly found may be class- 

 ified thus: 



1. Non-pathogenic; fermenting and various unclassified 

 micro-organisms. 



2, Pathogenic; tuberculosis, typhoid, cholera, scarlet 

 fever, diphtheria, and suppurative diseases have all been 

 spread by the agency of milk. 



I. The Fermentation Bacteria 



At the most we can make a merely provisional classifica- 

 tion of these processes. Many of them are intimately re- 

 lated. Of others, again, our knowledge is at present very 

 limited. It may be advisable, before proceeding, to con- 

 sider shortly what are the constituents of milk upon which 

 living ferments of various kinds exert their action, A 

 tabulation of the chief constituents would be as follows: 



r (i) Water 87.5 per cent. 



Ordinary 1 (2) Milk-sugar 4.9 



■esh milk = 

 100 per cent. 



y 



fresh milk = \ (3) Fat '^.6 



(4) Proteids (casein, etc.). . 3,3 

 {5) Mineral matter 0.7 



lOO.O 



Another mode of expressing average milk constitution 

 would be thus: 



Fat 4. 1 per cent. 



Solids not fat 8.8 " " 



12.9 " " 



It is probably too obvious to need remark that milks vary 

 in standard, but the above figures may be taken as authentic 

 averages. 



