THE CARRIER 



1329 



bodies, Gram-positive, grouped in pairs, var5dng in size from 0-3 /x 

 to 0 5 ft, capable of passing through Berkefeld N and V filters. 



The Carrier. — With regard to the spread of the disease, there was 

 a great conflict of opinion as to whether it was infectious; most 

 certainly it does not cross air-spaces, though it seems to be associated 

 with bedding, fomites, furniture, and dirt, which causes the 

 suspicion that the agent may be an animal parasite. Moreover, 

 the fact that it only appears in the cool season of the tropics, 

 and its rapid disappearance in the warm season, is. also in favour 

 of its transmission by some animal. Its non-infectious nature 

 has been proved by Jiirgens keeping twenty healthy men confined 

 with twenty typhus patients freed from lice, with negative results ; 

 therefore suspicion is aroused that it may be spread by a blood- 

 sucking parasite, perhaps an insect. 



Patton has shown that Clinocoris lectularius Linnseus, 1758, is 

 found along the north-west frontier of India; and Husband and 

 MacWalters draw attention to the fact that the distribution of this 

 bug curiously coincides with the distribution of typhus in India. 



These latter observers point out that in an epidemic occurring 

 in a gaol, the hospital was found infected with bugs, which occurred 

 nowhere else. On the destruction of these pests the epidemic 

 ceased. Moreover, they draw attention to the fact that predisposing 

 causes of typhus, such as dirt, overcrowding, and the way in which 

 the infection hangs about bedding, buildings, and furniture, are 

 easily explicable on the bug hypothesis. Sambon, in his article on 

 Rocky Mountain fever in Allbutt and Rolleston's ' System,' advances 

 arguments in favour of the identity of Rocky Mountain and typhus 

 fevers; but Husband and MacWalters' researches are not in favour 

 of a tick being the carrier of the disease. It may be that typhus 

 and Rocky Mountain fevers are caused by allied protozoan parasites 

 spread by different blood-suckers. In Glasgow the flea was sus- 

 pected to be the cause of the dissemination of the disease. Nicolle 

 suspected Pediculus corporis, and this was soon confirmed on 

 epidemiological grounds, which Crawford supported by a study of the 

 history of the epidemics. 



In 1909 Nicolle, Comte, and Conseil transmitted the virus from 

 infected monkeys to non-infected monkeys by means of the bites 

 of lice, Pediculus corporis de Geer, 1778. In 1910 Ricketts and 

 Wilder found that they could immunize monkeys against infection 

 with virulent blood by the bites of infected lice. In 191 1 Wilder 

 showed that lice became infective between the second and fifth day 

 after feeding, thus proving that the causal agent had undergone some 

 sort of development in the louse. In 1912 Anderson and Goldberger 

 supported Wilder, and concluded that P. humanus Linnseus, 1775, 

 andP. corporis de Geer, 1778, could both become infected, and that 

 this infection could be transmitted by the crushed insects or by their 

 bites. In 1914 Sergent, Foley, and Vialatte found cocco-bacilli in 

 lice, and in the same year Prowazek and Rocha-Lima found short 

 elliptical coccal bodies and rods. In handling the infected lice both 



84 



