MODE OF SPREAD OF THE DISEASE 505 



of two to three months before any notable change occurred in 

 the milk. Agglutination is usually given by the milk of infected 

 animals, and this property was always present when the micro- 

 coccus was found in the milk. It was, moreover, found that 

 monkeys and goats could be readily infected by feeding them 

 with milk containing the micrococcus, the disease being contracted 

 by fully 80 per cent, of the monkeys used. It was therefore 

 rendere'd practically certain that the human subject was infected 

 by means of such milk, and the result of preventive measures, 

 by which milk was excluded as an article of dietary amongst 

 the troops in Malta, has fully borne out this view. After such 

 measures were instituted, the number of cases in the second 

 half of 1906 fell to 11 per thousand, as contrasted with 47 

 per thousand in the corresponding part of the preceding year ; 

 further successful results have followed. Various facts with 

 regard to the epidemiology of the disease have thus been cleared 

 up. For example, it is more prevalent in the summer months, 

 when more milk is consumed ; and there is a larger proportion 

 of cases amongst those in good social position, the officers, for 

 example, suffering more in proportion than the privates. Another 

 interesting fact, pointed out by Horrocks, is that the disease has 

 practically disappeared from Gibraltar since the practice of im- 

 porting goats from Malta has stopped. The manner in which 

 the disease spreads from goat to goat has not yet been satis- 

 factorily determined. It has recently been found that the sheep 

 may be the subject of infection and that the micrococcus may be 

 excreted in its milk. It remains to be seen to what extent this 

 obtains. 



The work of the Commission, so far as it has gone, has been 

 to exclude other modes of infection than the ingestion of infected 

 milk as being of practical importance ; if the disease is conveyed 

 by contact at all, this is only when the contact is of an intimate 

 character, and even then it is probably of rare occurrence. Al- 

 though numerous patients suffering from the disease come to 

 England, there is no known case of fresh infection arising under 

 natural conditions. 



There is distinct evidence that the disease may be acquired by 

 inoculation through small lesions in the skin, and this method 

 is probably not infrequent amongst those who handle infected 

 milk. It has been shown that the organism may remain alive 

 in the bodies of mosquitoes for four or five days, and possibly 

 these insects may occasionally be the means of carrying the 

 disease ; there is no evidence, however, that this takes place 

 to any extent. 



