246 BACTERIOLOGY FOR NURSES 



ing infection ; hence the necessity for the immediate administra- 

 tion of antitoxin. For, once the toxin has entered into a firm union 

 with the nerve cells it cannot be displaced. Antitoxin in sufficient 

 amounts will neutralize the toxin as quickly as it is produced and 

 thus protect the nerve tissue until the leukocytes and other body 

 cells have destroyed the bacilli and spores. Unfortunately treat- 

 ment is often deferred until symptoms have appeared. In such 

 cases all the antitoxin can do is to combine with the free toxin 

 and prevent further damage. As a therapeutic measure injec- 

 tions are usually made intravenously or by means of a lumbar 

 puncture in order that the effect may be as speedy as possible. 

 In acute cases 50,000 to 100,000 units are administered during 

 the first few days. A prophylactic dose is usually 1000 units 

 injected subcutaneously or intramuscularly. 



The method of preparing tetanus antitoxin for the purpose 

 of passive immunization is described in Chapter II. 



Bacillus Welchii (B. Aerogenes Capsulatus). The name applies 

 rather to a group than to an individual organism. Welch and 

 Mittal in 1892 were the first to isolate and describe minutely a 

 member of the group, and they gave to the organism the name 

 B. aerogenes capsulatus. It is frequently spoken of, however, as 

 the Welch bacillus. Strains of bacilli closely related to and prob- 

 ably identical with the Welch bacillus have been described, among 

 which are B. phlegmonis emphysematosi, B. perfringens, B. 

 enteritidis sporogenes, and a number of others. During the recent 

 war the bacilli have been recognized as the most important agents 

 in the production of gas gangrene in infected wounds. 



Morphology and Staining. B. Welchii is a comparatively 

 large bacillus measuring from 4 to 6 ft in length and relatively 

 thick. In preparations from tissues or body fluids a distinct 

 capsule is seen surrounding it ; hence its original name. Spores 

 are formed by some strains and are most likely to appear when 

 blood serum is used as a medium. 



Cultivation. On agar the colonies are round with smooth 

 margins and no outgrowths. The bacillus ferments glucose, 

 saccharose, lactose, and maltose with the production of acid and 



