224 MEDICAL BACTERIOLOGY 



A "unit" of diphtheria antitoxin is 200 times the amount necessary to neu- 

 tralize one M.L.D. of toxin. 



Diphtheria antitoxin is employed as a prophylactic and as a curative agent. 



When given as a prophylactic the immunity to infection conferred is a 

 passive immunity and hence lasts only a few weeks. 



Diphtheria antitoxin is specific for the treatment of diphtheria. The earlier 

 it is given in the disease the better the results. 



When given as a prophylactic and in mild, early cases of the disease it is 

 injected subcutaneously, preferably in the left side of the abdominal wall. 

 In late, severe cases it is injected into a vein. 



The prophylactic dose is from 1000 to 2000 units, the curative dose from 

 10,000 to 40,000 units; repeated, if necessary. 



TETANUS ANTITOXIN 



Tetanus antitoxin is produced in practically the same way as diphtheria 

 antitoxin. Selected horses are injected at intervals with increasing amounts of 

 tetanus toxin (nitrate from bouillon culture of tetanus bacillus) until maximum 

 immunity is acquired. The horse is then bled and the blood serum collected. 



The American unit of tetanus antitoxin is 10 times the amount necessary to 

 immunize a 35o-Gm. guinea-pig against 100 times the M.L.D. of toxin. 



Tetanus antitoxin has its greatest value when employed as a prophylactic, 

 injected subcutaneously near the wound as soon as possible after the occurrence 

 of a wound or trauma likely to be infected with the tetanus bacillus, such as 

 black powder burns, deep puncture wounds inflicted by splinters of wood from 

 old buildings, rusty nails or instruments contaminated with garden soil, stable 

 dirt or hide dust. 



The prophylactic dose is from 1000 to 2000 units; this may be repeated in a 

 week if deemed necessary. 



When symptoms of tetanus have developed, antitoxin seldom prevents a 

 fatal result; it must be used in heroic doses, preferably injected into the spinal 

 canal. 



ANTISTREPTOCOCCUS SERUM 



Antistreptococcus serum is produced by injecting horses with killed and 

 attenuated streptococci until maximum immunity is acquired. As many differ- 

 ent strains of streptococci as can be procured are used, to produce a polyvalent 

 serum. 



The immunizing power of such serum is said to depend upon the opsonin 

 content. 



No definite dosage has been established. Large quantities are required to 

 obtain therapeutic effect, an initial dose of 100 to 200 cc., followed by repeated 

 doses of 10 to 20 cc. every 4 hours, if the first dose proves beneficial. 



Antistreptococcus serum should be injected deep into the muscles. 



The indications for its employment are said to be acute, severe primary and 

 secondary streptococcus infection. 



