272 BACILLUS OF TETANUS 



deep puncture wounds or ragged wounds of the hands (Fourth of July 

 injuries). In both man and the horse natural tetanus infection 

 almost invariably leads first to spasms in certain groups of muscles 

 and then progresses symmetrically to the other muscles of the body. 

 The period of incubation varies in the horse from four to five days 

 up to three weeks. According to Behring, one of the earliest and 

 most important symptoms occurs in the membrana nictitans of the 

 eye, which, when the head of a horse sick with tetanus is raised, is 

 found to cover about one-half the eyeball and to spread as the disease 

 progresses. The head and neck of the animal are elevated until the 

 upper border of the neck describes a straight line; in extreme cases it 

 is even concave, and forms what is called a deer neck. Mastication is 

 difficult in consequence of the trismus of the muscles of mastication, 

 and finally becomes impossible. The nostrils are dilated. The tail 

 in consequence of the contraction of its extensor muscles is stiffly ele- 

 vated. Finally the spinal column is curved (in opisthotonos position), 

 and the muscles of the neck and thorax become stiff and very hard. 

 All reflexes are accentuated, and a slight irritation will bring about 

 convulsions. Death results from progressive dyspnea. Cattle and 

 sheep also suffer from tetanus, but not nearly as frequently as horses. 



Tetanus in Laboratory Animals. The picture of tetanus is different 

 when small laboratory animals, such as guinea-pigs and rabbits, 

 are inoculated subcutaneously or intramuscularly. In this case the 

 contractions begin in the group of muscles located nearest the point of 

 injection. If the inoculation, for example, has been made into one of 

 the hind legs it is the first to be affected, and in succession the other 

 hind leg, the front legs, and, finally, the muscles of the back become 

 involved. Increase of reflex irritability generally does not occur, 

 but if it does it is observed only shortly before death. It has been 

 noticed that tetanus bacilli when inoculated experimentally do not 

 multiply at the place of inoculation; on the contrary, soon decrease 

 in numbers. The disease is produced by the absorption of the 

 toxins of the bacillus. Tetanus is one of the best examples of a pure 

 toxemia. 



Tetanus Toxin. Tetanus toxin, like that of diphtheria, is soluble; 

 it easily goes into solution if the bacilli are raised in a fluid culture 

 medium. They must, however, be kept under strictly anaerobic con- 

 ditions, because only under these will they produce a large amount 

 of toxins. If air is present the bouillon will be of low toxic value. 

 An ordinary slightly neutral bouillon containing 1 per cent, of 

 peptone and 0.5 per cent, of sodium chloride is a good medium, 

 but it must contain neither glycerin nor sugar, because the resulting 

 acid formation will interfere with the toxin production. As the 

 latter does not proceed very abundantly during the first few days of 

 growth the cultures must be kept under anaerobic conditions in the 

 incubator for ten or more days. The bacteria are removed from 

 the bouillon by filtering it through a Pasteur-Chamberland filter 



