SERUM TREATMENT OF TETANUS 721 



Even though the toxin gains entrance to the blood, it cannot injure 

 the motor nerve tissue directly, as, for example, by means of the blood- 

 vessels supplying the central nervous system. As was previously stated, 

 the toxin in the blood and lymph channels may reach the central nervous 

 system only in an indirect manner, through the end-plates or lymphatics 

 of other motor nerves. 



Ascending centripetally along the motor plates and lymphatics, the 

 poison reaches the motor spinal ganglia on the side inoculated; it then 

 affects the ganglia on the opposite side, making them hypersensitive. 

 The visible result of this hypersensitiveness is the highly increased muscle 

 tonus i. e., rigidity. If the supply continues, the toxin next affects 

 the nearest sensory apparatus: there is an increase in the reflexes, but 

 only when the affected portion is irritated. In the further course of the 

 poisoning the toxin as it ascends continues to affect more and more 

 motor centers and also the neighboring sensory apparatus. This leads 

 to spasm of all the striated muscles and general reflex tetanus (Park). 



3. Regardless of the severity of the infection, there is always an in- 

 cubation period in tetanus during which the bacilli multiply and produce 

 toxin which is traveling toward the tissues of the central nervous system. 

 Antitoxin in sufficient amount will neutralize the toxin as quickly as it is 

 produced, and thus protect the infected individual until the leukocytes and 

 other body-cells have destroyed the bacilli and spores. 



In general terms, the severer the wound and the heavier the infec- 

 tion, the shorter will be the incubation period and the higher the mortal- 

 ity. In acute tetanus the incubation period is less than ten days; in 

 chronic tetanus this period is much longer and more variable. 



The toxin is produced, and may be absorbed during or at least soon after 

 the first twenty-four hours following infection; this explains the necessity 

 for administering antitoxin as soon as possible after the injury has been 

 received. 



Action of Tetanus Antitoxin. 1. Tetanus antitoxin will neutralize 

 free toxin in a chemical manner similar in some respects to that by which 

 neutralization of an acid by an alkali is effected. It is generally believed 

 that as spon as the molecule of antitoxin has become united with a mol- 

 ecule of toxin, the latter is rendered inert. It may be possible, however, 

 for the toxin molecule to become dissociated and attack nerve-cells or 

 other molecules of antitoxin; this is one reason for the necessity of giv- 

 ing large doses of antitoxin in order than an excess may be at hand. 



2. When tetanus toxin has once united with nerve-cells, it is difficult 

 or impossible for the antitoxin to effect its neutralization. Hence the 

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