Anatomical Changes, Symj^toms. 449 



and the different organs; when external injuries cannot be found great care should 

 be exercised in the inspection of the canals and cavities lined with mucous mem- 

 branes, especially the nasal cavity, the pharynx, the gums, and the uterus. In a 

 case reported by Merkel the infection was occasioned by a wheat kernel that had 

 entered the air passages, while Hengst traced the infection in a cow back to an 

 injury of the paunch by a wire. 



The infectious nature of suspected material may be ascertained with certainty 

 by subcutaneous or intramuscular inoculation of pus or necrotic pieces of tissue 

 into guinea pigs or mice. This is not so easy by microscopic examination; however 

 the spore-bearing tetanus bacilli are found in the inflammatory products and the 

 diseased tissues associated with other organisms. (See Fig. 73 on page 457.) 



Symptoms. The period of incubation after subcutaneous, 

 intramuscular or intraperitoneal injection of a medium-sized 

 amount of virus into smaller animals is about 2 to 5 days and 

 in larger animals longer; its duration depends on the strength 

 and quantity of the toxin, less so on the susceptibility of the 

 animal. Under natural conditions the first symptoms have 

 been noted as early as 24 hours after infection (mostly in very 

 young animals) ; as a rule the inculcation lasts longer, and in 

 the majority of cases, especially in horses, it is 1 to 2 weeks. 



From Cadiot's compilation of 38 horses suffering from tetanus the di 

 occurred at the end of the first day in one case, on second to fifth day in six eases, 

 fifth to tenth day in 13 cases, tenth to twentieth day in 15 cases, twentieth to 

 thirtieth day in three cases. According to Hoffmann the period of incubation in 

 parturition tetanus in cows is 2 to 14 days, in rams and boars after castration 

 8 to 14 days, in lambs after pox vaccination 13 to 18 days. — Dieudonne reports on 

 58 cases of tetanus following docking of the tail, where the incubation lasted 

 8 to 42 days. — In a cas-e of Boeder's a calf was attacked by the disease immediately 

 after birth and died on the fifth day, while De Bruin noted in a colt that had stepped 

 on a rusty nail on the day of birth the first symptoms of tetanus two days after 

 the accident. Rietsch performed artificial inoculation and observed a period of 

 incubation of 15 days in mules; Kitt observed it in sheep to be 6 to 7 days, and 

 in dogs 2 days. 



Excluding the rapidly developing cases where the disease 

 is completely developed within a few hours, the beginning 

 of the disease causes no change whatever sometimes for 1 to 

 2 days, with the exception of a disinclination of the animals 

 to move and a sluggish action when they are prodded. The 

 legs bend less than normally and the extremities are raised 

 stiffly, while feeding is prolonged, the animals appearing to 

 chew much more carefully and apparently having some difficulty 

 in swallowing food ; at this stage the peculiar projection of the 

 head and the rigid station and immobility of the ears may be 

 noted. These symptoms indicate beginning spasm of individual 

 muscle groups, which, in the majority of cases, appears first 

 in the head or neck, less frequently in the hindquarters and 

 from here spreads forwards or back^vards. In some cases the 

 spasm begins in the muscles nearest to the site of infection, 

 as is the case in artificial subcutaneous inoculation. In rare 

 cases the spasm may be confined to a certain region of the body, 

 for instance the hindquarters (T. parietalis) ; usually it is uni- 

 versal (T. universalis), in which case the infected animals have 

 a characteristic appearance. 



