BACILLUS TETANL 543 



lished, the circulating blood contains a body, antitoxin, 

 that combines directly with tetanus toxin in a test-tube, 

 and thereby renders it physiologically inactive (non-in- 

 toxicating) ; and the serum of the immune animal is 

 not only capable of protecting non-immune, susceptible 

 animals from the poisonous action of tetanus toxin 

 (within limits), but also against the effects of the living 

 tetanus bacillus as well. 



Tetanus antitoxin, though the first antitoxin discov- 

 ered and frequently employed in the treatment of 

 tetanus, has not yielded as brilliant results as those 

 obtained with diphtheria antitoxin. There are two 

 important reasons why tetanus antitoxin may never be 

 expected to yield such satisfactory results as does 

 diphtheria antitoxin. First, diphtheria infection can be 

 diagnosed by bacteriological methods and the antitoxin 

 administered long before any very marked constitutional 

 symptoms have developed, and consequently long before 

 the diphtheria toxin has had time to bring about very 

 serious tissue alterations. In tetanus it is impossible to 

 make such a definite bacteriological examination, and 

 very frequently the first manifestation of the disease is 

 the twitching of the muscles which is the antecedent 

 sign of the tetanic convulsions. When these clinical 

 manifestations have developed in tetanus there is already 

 very serious involvement of the central nervous system 

 by the action of the tetanus toxin upon the nerve cells. 

 The second reason why tetanus antitoxin is likely to 

 prove less helpful than diphtheria antitoxin is that the 

 tetanus toxin seems to have very great affinity for the 

 cells of the central nervous system, while the cells and 

 tissues of the body affected primarily by diphtheria toxin 

 are of far less vital importance. 



