THE SERUM TREATMENT OF DIPHTHERIA. 519 



An animal injected with the antidiphtheritic serum becomes 

 refractory to diphtheria almost immediately; but the immunity 

 does not last, as it diminishes from time to time, disappearing in 

 some days or weeks according to the strength and the quantity 

 of the serum administered. 



To give an idea of the strength of the serum used in his exper- 

 iments on children and animals, Roux stated that one tenth of a 

 cubic centimetre, about a drop and a half, of the toxine he em- 

 ployed would kill a guinea pig weighing five hundred grammes, 

 or one pound, in forty-eight hours ; but a mixture of one tenth of 

 a cubic centimetre of this serum with nine tenths of a cubic centi- 

 metre of those toxines did not even cause a local effect in the 

 guinea pig that received it. In other words, a dose of toxine that 

 would suflQce to kill nine average guinea pigs was rendered inert 

 by one ninth of its quantity of serum. Experiments on animals 

 have shown that where the toxine is introduced first it is neces- 

 sary to give more of the serum, and after a certain delay the 

 serum exercises no antagonistic effect on the toxine that was 

 administered. 



The preceding facts have served to bring us to the considera- 

 tion of the use of the serum in the treatment of diphtheria. The 

 prevalence of the latter disease may be judged from the reports 

 of the United States census of 1880 and of 1890, the statistics of 

 the former year showing that diphtheria and croup caused 77*96 

 deaths per thousand deaths, and those of the latter year showing 

 that they caused 49 "54 deaths per thousand deaths. This experi- 

 ence of a lessening of the mortality from diphtheria has not been 

 confirmed by the statistics of New York city, in which there was 

 a rise and fall from 1883 to 1892 inclusive : 



1883 48-60 



1884 52-46 



1885 6109 



1886 '72-15 



1887 VS-iQ 



Mortality per Thousand of Deatlis. 



1888 63-54 



1889 59-55 



1890 44-46 



1891 45-12 



1892 47-55 



In fact, it may be noticed that the year the census statistics 

 were obtained the mortality in the city of New York was less 

 than in any other year of the series. This oscillation has occurred 

 in other countries. Thus, in England, during the decade 1861 to 

 1870 the diphtheria mortality was one hundred and eighty-seven 

 per million living ; during the decade 1871 to 1880 it fell to one 

 hundred and twenty-one per million living ; while from 1881 to 

 1890 it increased to one hundred and fifty-nine per million; and 

 this increase was the more conspicuous because both the general 

 death-rate and the death-rate from infectious diseases had been 



