332 MICROBIOLOGY 



a solution of 1 to 1,000 bichloride of mercury for three hours. 



Pathogenesis. This organism is fatal to mice, rabbits, 

 guinea pigs, horses, goats and other animals. Bats and birds 

 are less susceptible and fowls rarely contract the disease. Man 

 is more susceptible than any of the animals that have been 

 tested. A horse is about six times as sensitive as a guinea pig 

 and 300,000 times as sensitive as a hen. If the experimental 

 animal is inoculated with a non lethal dose, a local tetanus 

 may be produced which lasts for some days or even weeks, 

 after which recovery occurs. 



Tetanus antitoxin. Like diphtheria, tetanus toxin when 

 injected causes a reaction on the part of the animal tissues 

 with the production of antitoxin. The tetanus antitoxin is 

 produced by the injection into horses of tetanus toxin in in- 

 creasing doses. The toxin is produced in bouillon cultures 

 grown anaerobically in the laboratory. After 15 days, the 

 culture is filtered through porcelain and the germ free filtrate 

 is injected. The horses receive an initial dose of 5 cc. of the 

 toxin with a sufficient amount of the antitoxin to neutralize it. 

 In 5 days the dose is increased and then every 5 to 7 days 

 larger amounts are given. The dose is increased as rapidly 

 as the horses can stand it, until they support 700 to 800 cc. 

 or more at a time. This amount should not be injected in a 

 single place, or severe and perhaps fatal local tetanus may 

 develop. After some months of this treatment the blood of 

 the horse contains the antitoxin in sufficient amount for 

 therapeutic use. 



Tetanus antitoxin is used in certain localities very ex- 

 tensively for immunizing against tetanus horses that have 

 received puncture wounds and in cases of operations where 

 the healthy skin is incised. It is also used therapeutically in 

 both man and animals. The results vary when it is adminis- 

 tered after symptoms appear. It is very effective, however, 

 as an immunizing agent. 



