202 APPLIED BACTERIOLOGY 



those serums are to be preferred in which the requisite 

 number of 'units' are contained in. a small volume, say 

 10 c.c. or less. 

 The conclusions arrived at are as follows : 



1. ' That a common standard of estimating the strength 

 of antitoxic serum should be agreed upon by the English 

 manufacturers. 



2. 'That no serum should ever be sent out containing 

 less than 60 normal antitoxic units per c.c. 



3. ' That antitoxic serum of higher strengths must also 

 be provided to meet the requirements of treatment in 

 more severe cases of diphtheria. 



4. ' That every sample of antitoxic serum sold should be 

 plainly marked with the antitoxic strength of the serum 

 (number of normal antitoxic units per c.c), the quantity of 

 serum present in the bottle, and the date of issue.' 



In many cases the injection of the serum is followed by 

 a speedy reduction in the severity of the symptoms, and a 

 rapid separation of the membrane in cases where it was 

 causing obstruction of the air-passages, thus diminishing 

 the number of cases which would otherwise require 

 tracheotomy. 



In taking into consideration the great reduction in the 

 mortality from diphtheria, it is necessary to take into 

 calculation the age of the patient, this being a very 

 important factor. Again, new methods of diagnosis may 

 also lead to errors in statistics. The diagnosis of the cases 

 treated by antitoxin has been verified by a bacteriological 

 examination, while in former times this plan has usually 

 been omitted. 



A bacteriological examination enables us now to exclude 

 from our statistics many cases of angina and croup which 

 would formerly have been included. These cases are less 

 severe than cases of true diphtheria, and on this account 



