TOXINS OF THE TETANUS BACILLUS 431 



When injected subcutaneously the toxin is partly absorbed into 

 the nerves, and thence finds its way to that part of the spinal 

 cord from which these nerves spring. This explains the fact 

 that in some animals the tetanic spasms appear first in the 

 muscles of the part in which the inoculation has taken place. 

 In man under ordinary circumstances the first symptoms appear 

 in the neck. After subcutaneous injection of toxin, part finds 

 its way into the blood stream, and if infected animals be killed 

 during the incubation period there is often evidence of toxin in 

 the blood and solid organs. In the guinea-pig there is little 

 doubt that tetanus toxin has an affinity solely for the nervous 

 system. In other animals, e.g., the rabbit, an affinity may exist 

 in other organs, and the fixation of the poison in such situations 

 may give rise to no recognisable symptoms. In such an animal 

 as the alligator, it is possible that while some of its organs have 

 an affinity for tetanus toxin its nervous system has none. 

 Tetanus toxin introduced into the stomach or intestine is not 

 absorbed, but to a large extent passes through the intestine 

 unchanged. Evidence that any destruction takes place is 

 wanting. 



Marie and Morax shed some important light on the mode of 

 action of tetanus toxin in studying the path of absorption when 

 the toxin was injected into the muscles of the hind-limb. The 

 sciatic nerve in a rabbit was cut near the spinal cord and toxin 

 introduced into the muscles of the same side ; after some hours 

 the nerve was excised and introduced into a mouse — the animal 

 died of tetanus. But if the nerve were cut near the muscles the 

 proximal part did not contain toxin, though no doubt it had been 

 surrounded by lymph containing toxin. If the same experiment 

 were performed and an excess of toxin injected into the other 

 limb, still only the nerve which was left in connection with the 

 muscle showed evidence of the presence of toxin. From this it was 

 deduced that the toxin was absorbed by the end-plates in the 

 muscle and not from the lymphatics surrounding the nerve. 

 The absorption by the nerve was fairly rapid, as one hour after 

 injection the toxin was present in it, and the toxin was shown 

 to be exclusively centripetal in its flow. Further observa- 

 tions were made on this subject by Meyer and Kansom, who 

 found that toxin is only absorbed by the motor filaments of a 

 nerve, for while tetanus could be produced by injection into a 

 mixed nerve like the sciatic, the introduction of a lethal dose into 

 such a sensory nerve as the infra-orbital was not followed by 

 disease symptoms. If a small dose of toxin be injected into the 

 sciatic nerve, it reaches the corresponding motor cells of the cord, 



