Man's Mortal Enemies 9 



Actually there are two forms of the disease: the true 

 bubonic plague, which one gets when he is bitten by a plague- 

 carrying insect; and the pneumonic plague, in which the 

 bacillus is carried directly from one person to another by 

 means of infected droplets. But, since the pneumonic form 

 is merely an outgrowth of the bubonic form of the disease, 

 as long as there are rats to act as a reservoir for plague and as 

 long as there are fleas to carry the plague to man, the pos- 

 sibility of tragic epidemics will always be with us. 



It is probable that most epidemics of human plague 

 started when fleas from plague-infested wild rats transferred 

 their place of abode to house rats, and the fleas from the 

 house rats, upon the death of their hosts, jumped over to 

 people. Yet, there is evidence that the rat flea is not the 

 only culprit. Cat and dog fleas, fleas on wild and domesti- 

 cated birds, and even bedbugs and lice may, under some con- 

 ditions, play a part in the spread of the disease. 



And that brings us back to the San Francisco epidemic 

 of 1900. This epidemic, as was mentioned before, had run its 

 course by 1904, at least as far as anyone then knew. But 

 only on the surface. Among the hordes of rats it was still 

 smoldering, and worse yet, it had spread from the rats to 

 other rodents — ground squirrels, rabbits, chipmunks, prairie 

 dogs, etc. — as was discovered in 1906. Since then, plague 

 has been found in wild rodents in all of the western states, 

 and in many parts of the east. So far, only a few cases a 

 year of human plague have been reported, and in all cases the 

 viaims were campers, hunters, and children who came in 

 contact with the wild rodents. But now that the war is over 

 and more and more people are vacationing in the wide-open 

 spaces, will the number of plague cases increase? Or will 

 fleas from the infected wild rodents carry the disease to our 



