MILK AS A CARRIER OF DISEASE. 203 



the dozen. The first reliable observation on this subject was made 

 by Ballard in 1870, when an epidemic of typhus broke out in 

 Islington, 67 houses and 167 patients being infected. A careful 

 investigation of all the cases led to its being traced to a farm- 

 house from whence the milk supplied to the infected families was 

 derived, and there the closet cesspool was found to communicate 

 (through rat-holes) with the well, the water from which was also 

 used for cleansing the milk-pails. To this first instance two others 

 of recent date may be added. One of them was investigated by 

 PAUL SCHMIDT (I.), and arouses interest because it treats of the 

 inmates of a prison, where communication with the outer world 

 is much easier to trace. In two prisons in Strassburg (Alsace), 

 where typhus had not recurred since the Franco-German war, it 

 broke out again in 1890, and that, too, among a section of the 

 inmates who had partaken of milk derived from a neighbouring 

 village where the disease was rife. The epidemic died out when 

 the supply of milk from this source was prohibited. A second 

 equally convincing instance was observed by REICH (I.) in 1892. 

 ROWLAND (I.) found living typhus bacilli in an Indian milk-comes- 

 tible (known as " Dahi "). The so-called explosive occurrence of 

 this rapidly extending pestilence in a healthy neighbourhood is 

 thus explained by the fact of its germs gaining access to the system 

 with the food. Finally, milk is also a carrier of certain diseases 

 that are recognised as infectious, but whose exciting agent has not 

 yet been discovered, e.g. scarlet fever a case of which is recorded 

 by W. H. POWER (I.) and foot-and-mouth disease. 



123. Boiling Milk. 



The particulars given sufficiently evidence the necessity for 

 killing the germs present in milk. Experience teaches that a 

 short boiling suffices to destroy the pathogenic organisms, the 

 tubercle bacilli being according to the researches of J. FORSTER 

 and C. DE MAN (I.), and of BONHOFF (I.) killed by the action of 

 a temperature of 



55 C. in 4 hours. 

 60 C. i hour. 

 65 C. 15 minutes. 



80 C. in 5 minutes. 



90 C. 2 



95 C. i minute. 



70 C. 10 



The cholera bacteria and typhus bacilli are, as proved by 

 GEUNS (II.), capable of still less resistance, and are therefore 

 killed much more quickly than the tubercle bacilli by a treatment 

 expressed by the above figures. Only a single pathogenic species 

 can withstand the short boiling to which milk is ordinarily sub- 

 jected in domestic management, and this is the anthrax bacillus 

 (spores). The danger incurred on this account is, however, slight, 

 since this microbe only forms spores in presence of oxygen, and 

 therefore not within (the arterial circulatory system of) the animal 



