1903.] Researches on Tetanus. 29 



The injection of toxine into the vagus of dogs was followed, in two 

 cases, by a considerable slowing of the pulse which, in one case, lasted 

 some four weeks. The effect, though small in proportion to the dose, 

 seems to indicate that the heart-retarding centres of the vagus are 

 susceptible to tetanus toxine. Except after injection into the vagus 

 we have never observed slowing of the pulse in tetanised animals. 



V. Exaggerated Reflexes and Muscular Rigidity. 



Our experiments show conclusively that the tonic rigidity of the 

 muscles and the exaggeration of the reflexes are due to entirely 

 different and independent processes. Eeflex tetanus is known to be a 

 discontinuous series of contractions of short duration. The tetanic 

 rigidity of the muscles, on the other hand, is a continuous and gradually 

 increasing shortening, which may however regress. This shortening, 

 when it has existed for 24 30 hours, is not affected by curare nor by 

 section of the nerve. 



As regards the exaggeration of the reflexes, the experiments 

 demonstrate clearly that this is at first strictly localised in the sensory 

 part of the reflex arc belonging to the rigid limb. It is as if this 

 point in the spinal cord were alone poisoned by strychnine. 



VI. A Theory of Experimental Tetanus Intoxication. 



A consideration of the observed facts has led us to adopt the follow- 

 ing explanation of the course of experimental tetanus : 



The toxine is taken up from the point of injection by the motor 

 nerves. Passing along these it reaches first the motor centres in the 

 cord and excites there an over-irritability, so that the discharges, which 

 in the norm only give rise to the so-called muscular tone, become 

 abnormally strong (though not reaching the maximum at first). The 

 extensors and flexors of the injected limb brace themselves more and 

 more and in the hind limbs the extensors tend to overcome the flexors. 

 This, however, takes place gradually, so that for a considerable time 

 voluntary and reflex movements can be executed. In short it may be 

 said that tetanic rigidity is an intensified muscular tone in the affected 

 limb. This tetanic contraction or retraction of the muscles is dependent 

 on sensory excitement only in so far as, according to Hering, every 

 motor impulse is peripherogen. At bottom it arises from a pathological 

 condition of the motor apparatus in the spinal cord. 



The excess toxine is next carried in the fibres of the cord to the 

 motor apparatus of the corresponding limb of the other side. After 

 a time, and if enough toxine has been given, the nearest connected 

 sensory apparatus of the reflex arc in the spinal cord is attacked, with 

 the result that the general reflex movements following irritation of the 



