138 GROWTH AND WORK OF PLANTS 



to clot and the antitoxic serum is withdrawn. Successive injec- 

 tions are made up to about nine months and blood is drawn from 

 the horse from time to time. The horse may then be given a rest 

 for a few months and used again. In recent years it is customary 

 to inject antitoxin into the horse along with the first doses, since 

 a much larger dose of toxin can be administered and the process 

 of making the desired strength of antitoxin is accelerated. The 

 antitoxin is injected into the patient suffering from diphtheria in 

 an early stage of the disease. This antitoxin checks the growth 

 of the bacillus and the disease runs its course in a much milder 

 form. 



223. Public duty in the preservation of health. With the 

 knowledge gained in the investigations as to the cause, prevention 

 and treatment of these germ diseases, it becomes the public duty 

 of every person to be familiar with the principal facts as to the 

 cause of disease, the means of infection and contagion, and to 

 use every care not only in the preservation of his own health but 

 in preventing the distribution of the germs which will communicate 

 the disease to others. It is well known, for example, that the 

 typhoid fever germs are taken into the system by drinking con- 

 taminated water or milk or by eating contaminated food. The 

 great epidemics of typhoid fever, where they have been traced, have 

 been found to originate from one or two isolated cases on the water 

 shed of the public water supply. Carelessness in throwing the 

 refuse from a patient where rains or melted snows carry the bac- 

 teria into the water supply has often resulted in an epidemic, since 

 many of those drinking from the public supply contract the 

 disease. All such refuse matter should be thoroughly disinfected 

 and then covered where there w r ill be no drainage into streams, 

 for even if it is not drained into a water supply, flies during the 

 warm season will carry on their legs myriads of the germs and 

 then deposit them on food. The hands of attendants as well as 

 other things in the sick room should be properly disinfected, since 

 contact of these with food or fruits or with vessels used for holding 

 milk or food leads to the contamination of these substances. 

 Nearly every typhoid epidemic shows two sources of infection, the 



