I 88 TETANUS 



lu guinea pigs inoculated with infected soil the incubation 

 period is usually not over forty-eight hours and often less than 

 that. Park has found that mice, guinea pigs, rabbits, rats, 

 horses, goats and a few other animals inoculated with pure cul- 

 ture have a period of incubation of from one to three days. In 

 man it varies from one to twenty days. There are, however, a 

 few exceptionally long periods reported. It has been noted by 

 Richter and others that the shorter the period of incubation the 

 more .severe the disease, the mortalitj' being over 90 per cent in 

 the first and about 50 per cent when the symptoms were slow 

 in appearing. 



^ 146. Symptoms. The first symptoms are often 

 obscure and may be overlooked for se\'eral daj'S or they may 

 be ushered in suddenly with violent and extensive tonic spasms. 

 The tetanic spasms usually begin in the muscles of the head 

 and neck, extending from these to the muscles of the throat, 

 trunk and extremities. It often happens that the spasms first 

 appear in the hind quarters and extend forward. There is 

 stiffness of the parts affected. If in the head, the muscles of 

 mastication are first attacked with spasms, while if the hind 

 quarters are first attacked, tliere are usually spasms of the 

 muscles of the tail. The muscles at the site of inoculation are 

 frequently the first to show spasms and, if the disease is of a 

 mild type, they may be the only ones to exhibit symptoms. 

 Friedberger and Frdhner have grouped the muscles which are 

 attacked with the more obvious effects upon the appearance 

 of the animal. They are as tbllows, viz.: 



(ij. The uinsdcs of viastication. The contraction of 

 the.se muscles is called trismus or " lockjaw." According to 

 the degree of contraction the jaws remain in more or less close 

 contact, rendering prehension or mastication difficult or im- 

 possil)le. 



(2). 'Jlie otlier muscles of the liead. These are spasmodi- 

 calh- contracted in different degrees. Spasms of the muscles 

 of the ears cause the ears to be " pricked " and their tips to be 

 drawn together ; of the recti muscles of the eyes, cause the 

 eyes to be retracted in the orbit with protrusion of the nictitat- 

 ing membrane ; of the nose, produce dilatation of the nostrils ; 



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