CL welchii toxins 193 



known in detail, and it is probable that hyaluronidase is 

 actually a mixture of enzymes. The result of hyaluronidase 

 action on hyaluronic acid is a great reduction in viscosity 

 accompanied by hydrolysis and liberation of N-acetyl- 

 glucosamine. The barrier to penetration is thus overcome 

 by those organisms, including CI. ivelcMi, which can excrete 

 hyaluronidase. 



5. The production of toxins 



It is not the proteolysis, gas or histamine production, or 

 hyaluronidase action of CI. welchii that eventually kills the 

 host, but the production of toxins by the organism. It is 

 possible to grow the organism in a suitable medium, filter 

 off the organism, and kill a host animal by injecting the cell- 

 free medium containing toxins elaborated by the organisms 

 during growth. The medium can be concentrated and 

 fractionated, and the toxin extracted in a highly purified 

 state. It has all the properties of a protein and its toxic 

 action is destroyed by heat. 



By fractional precipitation the " toxin " of CI. welchii, 

 Type A, can be divided into two: 



[a) a-ToxiN: this substance has three biological actions: 



1 . If it is mixed with a suspension of red blood corpuscles, 

 it brings about haemolysis or disintegration of the cells and 

 is consequently said to be " haemolytic." 



2. In its presence, tissue cells disrupt and the toxin is said 

 to be " necrotic." 



3. If minute amounts are injected into an experimental 

 animal, the animal dies within a few minutes, so that the toxin 

 is " lethal." 



(6) ^-ToxiN : this is also haemolytic, but is neither necrotic 

 nor lethal, except in comparatively large doses. The lethal 

 properties of CI. welchii reside mainly in the a-toxin. 



In the past there have been two main theories concerning 

 the possible nature of toxin action : (a) that toxins are enzymes 



CHKM. A. B. J3 



