412 DIPHTHERIA 



* 

 ment was coming into use it was observed that if during an 

 epidemic the supply of serum failed, the mortality at once rose, — 

 in two instances recorded it was doubled. It must here be re- 

 membered 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 statistics 

 from London fever hospitals, the recoveries after tracheotomy were 

 56 - 4 as compared with 32 '1 per cent, previous to the introduction 

 of antitoxin. A striking result in the same hospitals brought 

 out by the statistics was 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 occurred while the patient 

 was under observation, the treatment was nearly always begun 

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

 treatment should be commenced whenever the disease is recog- 

 nised clinically, and a bacteriological diagnosis should not be 

 waited for. Behring showed that in cases treated on the first and 

 second days of the disease the mortality was only 7 "3 per cent., 

 and this has been generally confirmed, whilst after the fifth day 

 it was of little service to apply the treatment. In order to 

 obtain such results, it cannot be too strongly insisted on that 

 attention should be given to the dosage. 



Variations in the Virulence of the Diphtheria Bacillus. — In 

 cultures on serum the diphtheria bacilli retain their virulence 

 fairly well, and strains which are active producers of toxin have 

 been found to retain this property practically unchanged for 

 several years. Roux and Yersin found that, when the bacilli 

 were grown at an abnormally high temperature, namely, 39 '5° C, 

 and in a current of air, the virulence diminished so much that 

 they became practically innocuous. They also found that the 

 virulence could often be restored if the bacilli were inoculated 

 into animals along with streptococci. If, however, the virulence 

 had fallen very low, even the presence of the streptococci was 

 insufficient to restore it. Further, in the case of freshly isolated 

 avirulent organisms, otherwise like diphtheria bacilli, the 

 general result is that attempts to render them virulent have 

 failed. (The virulence is tested by the amount of living bacilli 

 necessary to produce a fatal result on injection into a guinea-pig, 

 and is to be distinguished from the power of producing toxin in 

 a fluid medium ; as pointed out by Dean, the two properties 

 often do not correspond.) Arkwright has found that the 



