488 IMMUNITY. 



pletion substances normally present in the serum (complements). 

 Antitoxic sera belong to the first group, antibacterial sera to the 

 second. In all, however, the substance specifically developed 

 appears to have a combining affinity for the substance introduced 

 into the body — toxin, albumin, bacterium, animal cell, etc., as 

 the case may be. 



Therapeutic Effects of Anti-sera. — As will have been gathered, 

 the chief human diseases treated by anti-sera are diphtheria, te- 

 tanus, streptococcus infection, pneumonia, plague, and snake 

 bite. Of the results of such treatment most is known in the 

 case of diphtheria. Here a very great diminution in the mortality 

 has resulted. The diphtheria antitoxin came into general use 

 about October, 1894, and the statistics pubHshed by Behring 

 towards the end of 1895 indicate results which have since been 

 confirmed. In the BerHn Hospitals the average mortality for 

 the years 1891-93 was 36.1 per cent, in 1894 it was 21. i per 

 cent, and in January-July, 1895, 14.9 per cent. The objection 

 that in some epidemics a very mild type of disease prevails is 

 met by the fact that similar diminutions of mortality have 

 occurred all over the world. Loddo collected the results of 7000 

 cases in Europe, America, Austraha, and Japan, in which the 

 mortality was 20 per cent as compared with a former mortality 

 in the same hospitals of 44 per cent. It has also been observed 

 that if during an epidemic the supply of serum fails, the mortality 

 at once rises ; and in two instances recorded it was doubled. It 

 must here be remembered that from the spread of bacteriological 

 knowledge the diagnosis of diphtheria is now much more accurate 

 than formerly. Another effect of the antitoxic treatment has 

 been that when tracheotomy is necessary the percentage of 

 recoveries is now much higher, being 73 per cent instead of 27 

 per cent in a group of cases collected by the American Pediatric 

 Society. In the London fever hospitals since 1894 the recoveries 

 after tracheotomy have been 56.4 as compared with 32.1 per 

 cent previous to the introduction of antitoxin. One of the most 

 striking results obtained in tjie same hospitals is a reduction of 

 the death-rate in post-scarlatinal diphtheria from 50 per cent to 

 between 4 per cent and 5 per cent. As the disease here occurs 

 while the patient is under observation the treatment is nearly 

 always begun on the first day. It is a matter of prime importance 

 that the treatment should be commenced whenever the disease is 



