432 TETANUS 



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 Ransom 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 the larger 

 animals, where the nerve path is longest, the incubation 

 period is also longest. When intravenous injection is practised, 

 the occurrence of tetanus in a part of the body can be pre- 

 cipitated by the injection of a drop of normal saline into the 

 corresponding 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 promi- 

 nent factor in the recurring spasms. While no absorption of 

 toxin takes place by sensory filaments, they have found evidence 

 of affection of the sensory apparatus in the occurrence of what 

 they call tetanus dolorosus. This is a great hypersesthesia and a 

 paroxysmal hyperalgesia which can be caused by injecting toxin 

 into the spinal cord or into a sensory root on the spinal side of 

 the posterior root ganglion. These symptoms are unaccompanied 

 by motor spasms, but the animal may die from exhaustion. The 

 same observers, in investigating the action of antitoxin, found 

 that its injection into a mixed nerve could prevent toxin 

 from passing up to the cord, but that if antitoxin were 

 injected even in great excess intravenously, and a short time 

 thereafter toxin were introduced into a nerve, death was not 

 prevented. This they attribute to the fact that antitoxin can 

 only neutralise the toxin which is still circulating in the blood. 

 This is a very far-reaching conclusion, as it throws doubt on 

 what has been held to be a possibility, namely, that toxin can 

 be actually detached from cells in which it is already anchored. 

 But a still more significant observation was made, for in one 

 case of an animal actively immunised against tetanus, and which 

 contained in its serum a considerable quantity of antitoxin the 

 injection of toxin into the sciatic nerve was followed by tetanus. 

 This would appear to militate against Ehrlich's position that 



