GROUP OF SPORE-BEARING ANAEROBES 353 



be observed in stained sections. Hemorrhages in different organs 

 are an inconstant accompaniment of the disease. 



Immunity. The toxin of the tetanus bacillus is produced in 

 artificial media as well as within the body. For the preparation of 

 antitoxin the organism is grown in bouillon, under anaerobic con- 

 ditions, in an atmosphere of hydrogen, with surfaces of the medium 

 covered with paraffin or paraffin oil or with oxygen excluded in 

 some other manner. After incubation for a period of one or two 

 weeks the broth is filtered through porcelain. The toxin may be 

 prepared in dried form by precipitation with an excess of am- 

 monium sulphate. After standing overnight the brown scum is 

 removed and dried, first between hardened filter-papers, then in a 

 desiccator, pulverized, and preserved in a darkened refrigerator. 

 Various methods of purification have been devised, such that a 

 dried toxin may be prepared of which 0.00000025 gm. will prove 

 quickly fatal to a white mouse. As has been said, this toxin has 

 a peculiar affinity for the cells of the central nervous system. Two 

 poisonous constituents of the toxin have been differentiated 

 tetanolysin, which lakes the red blood-cells, and tetanospasmin, 

 which gives rise to the characteristic tetanus symptoms. 



In the preparation of antitoxin the unprecipitated broth is 

 used. The smallest amount of toxin that will certainly kill a 

 350 gm. guinea-pig in three to four days is taken as the unit 

 of toxicity. Increasing amounts of the toxin are injected at 

 intervals into a horse. The blood-serum of the immunized horse 

 contains the specific antitoxin. Many methods of standardization 

 of the antitoxin have been used. In the United States it is titrated 

 by guinea-pig injections against a standard toxin, sent out by the 

 Hygienic Laboratory of the Public Health and Marine Hospital 

 Service. It is used in both human and veterinary medicine, 

 principally as a prophylactic. The tetanus antitoxin has not 

 taken the place in the treatment of tetanus that is occupied by the 

 antitoxin specific for diphtheria in the treatment of that disease. 

 It seems that the symptoms of the disease are noted only after 

 the union of the toxin with nerve-cells; that is, after much of the 

 damage has already been accomplished. The injection of anti- 

 toxin then will doubtless neutralize any toxin present in the blood, 

 but cannot remove the toxin already bound to the nerve-cells. 

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