SYMPTOMS 269 



noted by Richter and others that the shorter period of incuba- 

 tion the more severe the disease, the mortality being over 90 

 per cent in the first and about 50 per cent when the symptoms 

 were slow in appearing. 



§ 193. Symptoms. The first symptoms are often 

 obscure and may be overlooked for several days 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, there are usually spasms 

 of the muscles of the tail. The muscles at the site of inocula- 

 tion are frequently the first to show spasms and, if the disease 

 is of a mild type, they may be the only ones to exhibit symp- 

 toms. Friedberger and Frohner have grouped the muscles 

 which are attacked with the more obvious effects upon the 

 appearance of the animal. They are as follows : 



1. The miisdes of mas{icaiio?i. 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 

 impossible. 



2. The other muscles of the head. These are spasmodi- 

 cally 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 ; 

 of the dilator of the upper lip, give an abnormal shape to the 

 opening of the mouth. The muscles of the tongue, of degluti- 

 tion and of the larynx are also usually attacked by spasms. 



3. The extensor muscles of the neck. Contraction of these 

 muscles causes a stiff, outstretched carriage of the head and 



