450 



Tetanus. 



In an advanced stage of the disease in the horse the animal 

 will remain with stiffened, widely separated feet, and with head 

 and neck extended in one position (Fig, 70). The ears stand 

 erect approaching one another; the eyes, whose pupils become 

 dilated, are drawn deep into the orbits and are immobile on 

 account of the spasm of the eye muscles, while the anterior 

 surface is largely covered by the prolapsed membrane nictitans 

 (particularly noticeable when the head is raised). The nasal 

 wings are drawn upwards and as a result the nostrils have 

 a trumpet like appearance. The mouth is held closed, with 

 the commissures usually drawn outwards and slightly upwards ; 

 it is difficult to overcome the spasm of the thick masseter 

 muscles so as to separate the upper and lower incisors 1-2 cm. 

 (lockjaw, trismus). The spasm of the constrictors of the 



Fig. 70. Tetanus. Generaliied muscular spasms in a horse. 



pharynx prevents swallowing of the saliva which runs from 

 the mouth in long tough threads. 



As the facial portion of the head is raised by the contrac- 

 tion of the neck and upper throat muscles, the animal stretches 

 the head forwards and upwards, while the neck is extended 

 in. a straight line or is slightly curved upwards, so that its 

 upper margin forms a concave, its lower a convex line 

 (deer neck). The abdominal muscles are also contracted and 

 the abdomen is in consequence more or less retractied. The 

 tail is held rigidly and slightly raised or usually pulled a little 

 to one side. 



The spinal column usually forms a straight line (ortho- 

 tonus) ; exceptionally, owing to unusually violent spasms of the 

 long back muscles there is formed a concave arch (opistho- 



