132 ESSENTIALS OF BACTERIOLOGY 



sanitarians that the death-rate from this disease has been re- 

 duced from 66 per 100,000 to 19 per 100,000 since the use of 

 antitoxin (Park). 



The strength commonly employed in human beings is 5000 

 units, and as much as 120,000 units may be given without 

 detriment in severe cases. If this amount is injected sub- 

 cutaneously and even intravenously into a child suffering 

 from diphtheria in the earlier stages (second to third day), 

 the disease is often arrested. The membrane begins to dis- 

 appear, and in two or three days has vanished. The con" 

 stitutional symptoms are likewise greatly influenced by the 

 injection. For prophylaxis and immunizing well persons 

 1000 to 3000 units are employed. 



In such conditions asasthma severe and fatal results have 

 followed the use of the serum, and some cases of peculiar sen- 

 sitiveness to horse serum (see Anaphylaxis) have been re- 

 ported, fatal results having occurred, but fortunately such 

 mishaps are exceedingly rare. 



The antitoxin has no influence on the bacteria themselves; 

 their virulence and length of residence in the body are not 

 lessened. 



Preparation of Antitoxic Serum. Horses are rendered 

 immune by gradually increased doses of diphtheria toxin, the 

 power of the toxin having first been standardized by its neu- 

 tralization with some standard antitoxin in powdered form. 



Preparation of Toxin. The bacillus is grown in veal broth 

 with an alkaline reaction. (Acids prevent toxin formation.) 

 There should be a free supply of oxygen, and, therefore, large 

 shallow flasks are used. The maximum toxicity is developed 

 in seven to ten days. The strength should be 3-^ c.c., fatal 

 for 5oo-gram guinea-pig. 



The toxin is at first injected subcutaneously, then intraven- 

 ously, and after several months' treatment a resistance is ob- 

 tained that will withstand 300 to 500 times the original lethal 

 dose. The horse is then bled, and from five to nine liters 

 withdrawn; this is then allowed to coagulate, and under very 

 careful precautions the serum is placed in sterile packages, 



