THE HACILLUS AXD THE HAC'I 7-. ilIOLOGY OF DIPHTHERIA 205 



this protective property, which it acquires about a week after the begin- 

 ning of the disease, and loses again in a few weeks or months. More- 

 over, the blood serum of many individuals, usually adults, who have 

 never had diphtheria often has a slight general antitoxic property. 



Antitoxic Serum. The knowledge derived from these remarkable 

 investigations into the protective powers of the blood serum of immu- 

 nized animals has been employed with the most brilliant results for the 

 prevention and early treatment of diphtheria in man. The discovery 

 of the method of the production of antitoxic serum or antitoxin in 

 animals, and its practical application to the treatment and cure of 

 diphtheria, has been shared by many experimenters, at first chiefly in 

 Germany and France, and later in this country. 



Results of the Antitoxin Treatment of Diphtheria. The conclusions 

 arrived at by Biggs and Guerard, after a review of all the statistics and 

 opinions published since the beginning of the antitoxin treatment in 

 1892, were as follows: 



"It matters not from what point of view the subject is regarded, if 

 the evidence now at hand is properly weighed, but one conclusion is or 

 can be reached whether we consider the percentage of mortality from 

 diphtheria and croup in cities as a whole, or in hospitals, or in private 

 practice; or whether we take the absolute mortality for all the cities of 

 Germany whose population is over 15,000, and all the cities of France 

 whose population is over 20,000; or the absolute mortality for New 

 York City, or for the great hospitals in France, Germany, and Austria; 

 or whether we consider only the most fatal cases of diphtheria, the 

 laryngeal and operative cases; or whether we study the question with 

 relation to the day of the disease on which treatment is commenced, 

 or the age of the patient treated; it matters not how the subject is re- 

 garded or how it is turned for the purpose of comparison with previous 

 results, the conclusion reached is always the same namely, there has 

 been an average reduction of mortality from the use of antitoxin in the 

 treatment of diphtheria of not less than 50 per cent., and under the most 

 favorable conditions a reduction to one-quarter, or even less, of the 

 previous death rate. This has occurred not in one city at one particular 

 time, but in many cities, in different countries, at different seasons of 

 the year, and always in conjunction with the introduction of antitoxin 

 serum and proportionate to the extent of its use." Except where im- 

 munization has been practical on a large scale no reduction in the 

 number of cases of diphtheria has been evident. 



Production of Diphtheria Antitoxin for Therapeutic Purposes. As a 

 result of the work of years in the laboratories of the Health Depart- 

 ment of New York City, the following may be laid down as a practical 

 method: 



A strong diphtheria toxin should be obtained by taking a very 

 virulent culture and growing it in broth under the conditions described 

 on page 194. The culture, after a week's growth, is removed, and 

 having been tested for purity by microscopic and culture tests is ren- 

 dered sterile by the addition of 10 per cent, of a 5 per cent, solution 



