BACTERIA 269 



and produce the tetanus symptoms in the absence of oxygen. 

 Opening such a wound to admit air, and disinfecting it with 

 a weak solution of bichloride of mercury will prevent its action. 

 Other bacterial diseases are pneumonia, influenza or la grippe, 

 anthrax, swine plague, etc. Many of these bacteria develop 

 and excrete toxic substances called toxins, which are very 

 poisonous. These act locally on the tissues, and in many 

 cases, as in diphtheria, are carried in the blood to all parts of 

 the system, cause the fever in the patient and often seriously 

 affect the heart and kidneys. The bacteria themselves are in a 

 number of cases finally checked in their growth or killed by these 

 same toxins which they excrete. This principle has led to an 

 important practice in the prevention and cure of some of these 

 diseases, i.e., by injecting what is called an antitoxin into the 

 blood. In the case of smallpox the bacteria are inoculated into 

 healthy cows and a mild form of the disease is developed. To 

 prevent smallpox in man some "virus" of the "cow pox" is 

 then inoculated into the system, or the person is vaccinated. 

 The result is a very mild form of the disease and the system is able 

 to resist it. But the distribution of the toxin in the system ren- 

 ders the person immune from the disease even in a virulent form 

 for a number of years. So in the case of certain contagious 

 diseases, as in cholera, if the patient recovers he is immune from 

 the disease for a period of years. 



In the case of diphtheria the antitoxin is obtained from the 

 blood of healthy horses in the following way. The toxin is first 

 obtained from pure cultures of virulent forms of the bacillus. 

 Successive subcutaneous injections of this toxin are made in the 

 horse every 5 to 7 or 3 to 7 days for a period of about three months 

 when blood is drawn from the jugular vein of the horse, allowed 

 to clot and the antitoxic serum is withdrawn. Successive injec- 

 tions are made up to about nine months and blood is drawn from 

 the horse from time to time. The horse may then be given a rest 

 for a few months and used again. In recent years it is customary 

 to inject antitoxin into the horse along with the first doses, since 

 a much larger dose of toxin can be administered and the process 



