TOXINS OF THE TETANUS BACILLUS 427 



plates in the muscle and not from the lymphatics surrounding 

 the nerve. It was further shown that a nerve in the process of 

 degeneration following section did not absorb toxin after the 

 manner of a normal nerve. By a similar method it was shown 

 that the absorption by the nerve was fairly rapid, as one hour 

 after injection the toxin was present in it, and from other 

 experiments the view was put forth that the toxin was centripetal 

 in its flow and did not pass centrifugally in a nerve to which it 

 artificially gained access. Further observations have been made 

 on this subject by Meyer and Ransom. These observers found 

 evidence 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, 

 and a local tetanus of the muscles supplied by the nerve results. 

 With a larger dose the poison passes across the commissure to 

 the corresponding cells of the other side, and if still further 

 excess is present it passes up the cord to higher centres. The 

 affection of such higher centres can be prevented by section of 

 the cord. Meyer and Hansom hold that when toxin is injected 

 subcutaneously or intravenously, it only acts by being absorbed 

 by the end-plates in muscles and thence passes to the cord, and 

 they consider that the incubation period is to be explained by the 

 time taken for this extended passage to occur. In this connection 

 they point out that it is in the larger animals" where the nerve 

 path is longest, that the incubation period is also long. Like 

 Marie and Morax, they believe that absorption of toxin by 

 its bathing the lateral aspects of uninjured nervous structures 

 does not occur. In support of this they bring forward the 

 observation that when intravenous injection is practised, the 

 occurrence of tetanus in a part of the body can be precipitated 

 by the injection of a drop of normal saline into the correspond- 

 ing part of the cord, sufficient injury being thus caused to allow 

 the toxin in the surrounding lymph to obtain access to the 

 nervous elements. With regard to the action of tetanus toxin, 

 Meyer and Ransom believe that there is a double effect on the 

 nerve cells first, an exaggeration of the normal tonus, which 

 accounts for the continuous stiffness of the muscles, and 

 secondly, an increase in reflex irritability, which is a pro- 

 minent factor in the recurring spasms. While no absorption 

 of toxin takes place by sensory filaments, they have found 

 evidence of atfection of the sensory apparatus in the 



