MO 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 
