ACTION OF TETANUS TOXIN. 413 



week, 45 per cent, in the second, and about 30 per 

 cent, in the third or fourth weeks. The shorter 

 the incubation period the more fatal the disease. 

 In the statistics cited the mortality with short in- 

 cubation was 91 per cent.; when the incubation 

 period was moderate it was 81.3 per cent., and 

 when prolonged, 52.9 per cent. The nearer the 

 infection atrium is to the central nervous system 

 the shorter is the incubation period; "head teta- 

 nus" develops quickly. 



The pathogenic properties of the tetanus bacil- 

 lus reside in its soluble toxins, of which two, teta- 

 nospasmin and tetanolysin, are known. The char- 

 acteristic nervous phenomena of the infection de- 

 pend on the action of the former, whereas the lat- 

 ter, a hemolytic toxin, is of minor importance. As 

 in diphtheria, a systemic distribution of the bacilli 

 is not necessary for the development of the dis- 

 ease, the toxin being produced by the organisms in 

 the wound, whence it is carried to the nervous 

 tissue by way of the lymphatics. Particularly in 

 mixed infections tetanus bacilli may be carried to 

 neighboring lymphatic glands and eventually 

 reach the circulation; pure cultures have been ob- 

 tained from the heart's blood in experimental 

 work. The blood, on account of its content in 

 oxygen, is thought to be unfavorable for the 

 growth of the organism. 



Just before death the toxin has been demon- 

 strated in the blood of man by injecting some of 

 the serum into mice. Its excretion in the urine is 

 questionable. Tetanus produces no characteristic 

 anatomic changes, although degenerative lesions 

 in the ganglionic cells occur. Death usually occurs 

 from asphyxia caused by contractions of the dia- 



