The fact that the plague already has such a start among the squirrels opens a new and very serious phase of the problem of suppressing the disease. All who have hunted the ground-squirrels will testify to the readiness with which the fleas from them will bite those who are handling them. As it is the sick or weak squirrels that are most often taken there is always a chance that plague may be transferred from them to human beings. The records of the plague cases in California show at least three cases in which there seems to be very little doubt that the disease resulted from handling plague-infected squirrels. [Illustration: FIG. 109--Human-flea (_P. irritans_); female.] [Illustration: FIG. 110--Mouse-flea (_Ctenopsyllus musculi_); female.] A still more serious thing is the possibility of the disease remaining in a more or less virulent form among the squirrels for some time, possibly for years, and then breaking out again in some locality where the rats or men may become infected. As long as there is a trace of the disease among the squirrels there is always the chance of it spreading, so that new areas may become infested. Those in charge of the plague-suppressive measures are fully aware of these dangers and are making a careful study of the situation and will doubtless be able to cope with it successfully. It may be that the squirrels will have to be exterminated in the infected regions. This would be a long and difficult task, but the success attending the fight against the rats in a great city shows what can be done when the determination to do it is there. REMEDIES FOR FLEAS We have seen how a great city set to work to rid itself of the plague-sick rats. As a matter of fact it was not the rats that they were after primarily. If the rats had not harbored fleas the city would have been glad to let the disease take its course and destroy as many rats as possible. But it was found that the only way to get rid of the fleas that might possibly be infected with the plague was to kill their rat hosts. General cleaning-up measures will of course very materially lessen the number of fleas about the private dwellings, but there often remains a number of fleas in the house that are a source of great annoyance even if the danger is eliminated. Particularly is this apt to be so in places where cats or dogs are members of the household. These animals almost always harbor at least a few fleas, and where there are a few there is always a possibility, even a great probability, that there will be many more unless an effort is made to get rid of them.