1896 THE MICROSCOPE. 39 



destroyed by cultures from diphtheria. On the other 

 hand, rats and mice are comjjletely immune against the 

 toxin of diphtheria. 



Acquired immunity usually follows a single attack of 

 most eruptive diseases, but not of erysipelas or diphthe- 

 ria. The whole subject of acquired immunity was opened 

 up by Pasteur's work in 1870 in chicken cholera. Anti- 

 toxin in the blood plays the all-imjiortant role of furnish- 

 ing immunity. Just how and why the blood of some 

 animals is naturally immune may never be known. It 

 has been thought that the acidity or alkalinity of blood 

 may furnish a clew, but thus far investigators have not 

 felt like hazarding an opinion. The resisting power of 

 certain animal blood is something marvelous, when it is 

 remembered that cholera toxin is 260 times stronger than 

 strychnine. 



One of the most valuable discoveries of recent years, at 

 a time when so many thousands are keenly alert to new 

 methods and new theories, is the discovery and successful 

 use of antitoxin in epidemics of diphtheria. During the 

 recent epidemic of that disease in Washington, Dr. 

 Rosenau had charge of the diphtheria hospital, and con- 

 sequently nearly every recorded case came under his 

 professional care or immediate notice. The antixoxin 

 treatment was used in every case, and with most encour- 

 aging results. To render the patient immune, or to neu- 

 tralize the effects of the disease, it is necessary that the 

 case be taken in its early stages, and that it should be 

 free from complications with other or kindred ailments. 

 When treated under such favorable conditions relief was 

 obtained in nearly every case. 



The mode of preparation of antitoxin has been made 

 public. A healthy horse is injected with the toxin of diph- 

 theria every few days for a period of one or two months, 

 or until no reaction follows. The blood is then drawn, 

 from the serum of which the antitoxin is made. 



