44 INFECTION 



Tetanus toxin is composed of two substances: tetanospasmin 

 and tetanolysin. The first unites chemically with the motor ele- 

 ments of the nervous system, producing degeneration and causing 

 tremendous contractions of the muscles governed by the nerves 

 involved. The second has the property of dissolving tissue, such 

 as blood cells. 



Tetanus toxin travels from the infected site to the cord by 

 way of the nerves; it is exceedingly poisonous; a single prick of 

 the finger with a needle moistened with toxin, has induced tetanic 

 symptoms. 



If tetanus toxin of known strength is mixed in a test-tube with 

 fresh brain substance of a guinea pig, the toxin is no longer toxic 

 for guinea pigs. This shows that there is a chemical union of 

 the toxin and the cells of the brain. Cells of other organs have 

 no such effect. This explains specific action of tetanus upon 

 nervous tissue. 



Aggressins. If tubercle bacilli are injected into the abdominal 

 cavity of a guinea pig, tuberculosis is produced. If the exudate 

 produced in the peritoneum, consisting of fluid and cells, be 

 sterilized and injected into another guinea pig, together with 

 some virulent tubercle bacilli, the animal will succumb in twenty- 

 four hours. If the exudate alone be injected no effect will follow; 

 if bacilli alone are injected, a tuberculous peritonitis will be 

 produced in a few weeks. It is the exudate plus bacilli that 

 does the harm. The exudate is, in this instance, the aggressin. 

 Bail, who originated the doctrine of aggressins, believes that a 

 bacteriolysin is produced, which, acting on the bacilli, liberates 

 an endotoxin, which paralyzes the polynuclear leucocytes, 

 inhibiting their action as phagocytes. 



By heating the exudate to 6oC. the aggressins are increased in 

 activity, and it has been found that small amounts are relatively 

 stronger than larger ones. 



This phenomenon has been explained by Bail in this way. He 

 assumes that there are two substances in the exudate, one is 



