122 MILK AND THE PUBLIC HEALTH CHAP. 



interesting in this connection. The streptococci of human origin, 

 for the most part, died out fairly rapidly when implanted into the 

 teats of goats, but only relatively so ; one strain, for example, 

 living for as long as twenty -six days after inoculation. One 

 striking exception was, however, met with. In the case in which 

 the streptococcus isolated from the spleen of a boy who died of 

 acute lymphadenitis was used to infect a goat's teat, it did not set 

 up any inflammation, but survived as a harmless (to the goat) 

 saprophyte for the whole duration of the experiment, extending 

 over seven months. During this period it had 'not caused any 

 inflammatory changes or alteration in the appearances of the milk, 

 nor had its biological characters become altered except in one par- 

 ticular, and that inconstantly. This streptococcus had originally 

 caused a secondary infection in a boy, with marked elevation of 

 temperature, and, no doubt, largely contributed to his death. We 

 have only to postulate the retention of its virulence for a while, 

 and this goat's milk, if drunk (and it was absolutely normal in 

 appearance), would be a potent disease factor. 



It may be suggested that, if we accept this view, the cow would 

 be a much more potent agent for the spread of disease than it now 

 is, seeing the ease with which organisms of human origin can be 

 implanted under present conditions upon cows' teats and udders. 

 This is not likely since, as pointed out, human streptococci for the 

 most part will not grow in or on a bovine habitat. Incidentally 

 it may be mentioned that the opposite is probably also true, since 

 the streptococci of bovine mastitis died out with extreme rapidity 

 in the writer's own throat, although the infection was extremely 

 massive in character. 



IV. The above hypothesis offers the best explanation of a 

 number of facts in connection with certain milk-borne sore throat 

 and scarlet fever outbreaks, which otherwise it is extremely difficult 

 to explain. For example, a noticeable feature of some of these 

 outbreaks is the prolonged period during which the milk was 

 serving as a vehicle of infection. If we have a purely human 

 source of infection we should rather expect a very sudden outbreak 

 of short duration, since a human source is not likely to be daily 

 infecting the milk over a long period. In the Guildford outbreak, 

 for instance, the milk was infectious for some seven to eight weeks. 

 While the infection probably started from a human source (the 

 farmer), we cannot, as Pierce points out, account for the pro- 

 longed infectivity of the milk, unless we postulate a continuous 

 infection of the cows' milk -producing organs from this human 

 source. The farmer was disabled and unable to milk, etc., for at 

 least a month. 



The conflicting views of the Hendon outbreak can be reconciled, 

 and only so, on the above hypothesis. For example : 



