140 HOUSEHOLD BACTERIOLOGY 



from diphtheria, taking the results the world over and 

 in a general way, has been reduced more than 50 per 

 cent, and, under the most favorable conditions, full 

 75 per cent. I need not dwell upon the significance of 

 this beneficent result in the saving of life and in the 

 relief of suffering. 



But there is another way in which diphtheria anti- 

 toxin has been of the greatest value ; that is, in the 

 prevention of the disease among those who have been 

 exposed to infection in families, schools, and other pub- 

 lic institutions. Under these conditions an injection 

 of the antitoxin beneath the skin has been the means 

 of warding off an attack of the disease in groups of 

 persons, some of whom without it must inevitably have 



We should be most ungrateful if we failed to recog- 

 nize the importance of this new relationship which has 

 been established between ourselves and our old and 

 ever-useful friend, the horse. We make him manu- 

 facture for us in the department of his interior that 

 protective stuff which we could otherwise secure only 

 by ourselves sustaining an attack of diphtheria, and 

 this, too, with the chances against success. 



We are now prepared to inquire how this curious 

 antitoxin acts in the body to produce these truly mar- 

 velous effects. Has the body kept secreted all through 

 these years of evolution some special mechanism, or 

 some chemical potency, by which all of a sudden it 

 can protect itself against so subtle and so special a 

 poison as this roving bacillus ? And if so, do we keep 



