432 



PLAGUE 



lymphatic glands, and thereafter by a general infection. The 

 lesions in the lymphatic glands correspond in their main 

 characters with those in the human subject, although usually 

 at the time of death they have not reached a stage so advanced. 

 By this method of inoculation mice usually die in 1-3 days, 

 guinea-pigs and rats in 2-5 days, and rabbits in 4-7 days. 

 Post mortem the chief changes, in addition to the glandular 

 enlargement, are congestion of internal organs, sometimes with 

 haemorrhages, and enlargement of the spleen ; the bacilli are 

 numerous in the lymphatic glands and usually in the sjpleen 



(Fig. 148), and also, 

 though in somewhat less 

 degree, throughout the 

 blood. Infection can 

 also be produced by 

 smearing the material 



on *^ e con j unct i va r 



mucous membrane of 

 thenose,andthismethod 

 of inoculation has been 

 successfully applied in 

 cases where the plague 

 bacilli are present along 

 with other virulent 

 organisms, e.g. in sputum 

 along with pneumococci. 

 FIG. 148. Film preparation of spleen of rat Rats and mice can also 

 after inoculation with the bacillus of plague, be infected by feeding 

 showing numerous bacilli, most of which either with pure cultures 

 are somewhat plump. .,, . ,, 



Stained with carbol-thionin-blue. x 1000. or ^^ P ieces of or g ans 



from cases of the disease, 



though in this case infection probably takes place through the 

 mucous membrane of the mouth and adjacent parts, and only 

 to a limited extent, if at all, by the alimentary canal. Monkeys 

 also are highly susceptible to infection, and it has been shown 

 in the case of these animals that when inoculation is made on 

 the skin surface, for example, by means of a spine charged with 

 the bacillus, the glands in relation to the part may show the 

 characteristic lesion and a fatal result may follow without there 

 being any noticeable lesion at the primary seat. This fact 

 throws important light on infection by the skin in the human 

 subject. The disease may also extensively affect monkeys by 

 natural means during an epidemic. 



Paths and Mode of Infection. Plague bacilli may enter 



