314 PA THOGENIC BA CTERIA IN MILK 



with infected water ; or contaminated dust obtains access to the 

 milk. 



Numerous observers have declared their belief that flies may 

 disseminate the germs of typhoid fever. Some of the most recent 

 evidence on this point comes from the American Encampments 

 in the Spanish War of 1898 (Reed, Vaughan, and Shakespeare^), 

 and the British Army in South Africa, 1 900-1 901 (Tooth 2), and 

 there can be no doubt that flies may carry infected matter from 

 person to person, and from infected persons to food and milk. 

 It is possible for the fly to carry the typhoid bacillus in two ways. 

 First and more commonly faecal matter containing the typhoid 

 germ may adhere to the fly's head, mandibles, legs, wings, or body, 

 and be mechanically transported. Secondly, it is possible that the 

 typhoid bacillus may be carried in the digestive organs of the fly 

 and be deposited with its excrement, but this has not been proved. 

 However actually conveyed, there can be little doubt of the readi- 

 ness with which the fly may carry germs from infective excreta to 

 milk. Ficker has recently made some interesting experiments 

 entirely confirmatory of these facts.^ 



In the same way the typhoid bacillus may be air-borne from 

 dried excreta to milk. Partially dried typhoid stools on the floor 

 may be sufficiently comminuted to form an infective dust, which 

 may readily float through the air and be deposited in milk. In 

 a general way it may be said that epidemics set up by flies, and 

 by dissemination of the typhoid germ in the form of dust, are more 

 likely to occur during late summer and autumn. 



Finally, it should be remembered that the typhoid bacillus will 

 retain its vitality in milk for thirty days or longer, or until it is 

 destroyed by the growth of other organisms. The presence of 

 lactic fermentation or of the Oidium lactis does not interfere with 

 the growth of the typhoid bacillus. It flourishes in milk at 20° C. 

 or at 37° C. and does not alter the appearance of the milk.* A given 

 sample of milk may become infected after it has been boiled or 

 sterilised, and still afford a suitable nidus for the rapid and abundant 

 growth of the bacillus. Care must therefore be taken to protect 



* American War Department : Official Report, 1900; see also "A contribu 

 tion to the Study of the Insect Fauna of Human Excrement," by L. O. Howard 

 — Proc. Washington Academy of Science, vol. ii., pp. 541-604. 



2 Brit. Med. Jour., 1901, vol. i., pp. 642, 770 et seq.; and Ibid., 1902, vol. ii 

 pp. 936-941 (Firth and Horrocks). 



^ Archiv. f. Hyg., t. xlvi., 1903, pp. 274-283. 



* Local Government Board Report, 1896-97, pp. 243-254 (E. Cautley) ; Ibid. 

 1899-1900 (Klein). 



