378 DISEASES INVOLVING NERVOUS SYSTEM 



mouth is held shut with the commissures drawn upwardly. 

 From a spasmodic contraction of the masseter muscles it may 

 be impossible to open the mouth more than a fraction of an 

 inch (trismus). Due to a contraction of the constrictors of 

 the pharynx dysphagia and ptyalism are present. While in 

 most cases the back is held straight and rigid, occasionally it 

 is arched downwardly (opisthotonos) or still more rarely 

 curved laterally (pleurothotonos) . Locomotion is difficult, 

 the limbs being advanced stiffly and the feet barely raised 

 from the ground. It is almost impossible to back the horse. 

 The muscles are tense and hard, individual muscles standing 

 out prominently. Twitching of the muscles is a symptom 

 often noted. These symptoms may subside temporarily pro- 

 vided the patient is in no way excited. However, any sudden 

 noise, a flash of bright light or an unaccustomed sight will 

 cause the spasms to return. If the patient is struck with the 

 hand a paroxysm of muscular contraction passes over the 

 body. The mind of the patient is clear, although the face 

 shows anxiety and a peculiar rigid stare. Sometimes in 

 stallions the penis is erected. The pulse is small, the artery 

 hard. In severe cases the heart beat is rapid and often 

 palpitating. The respirations are increased three to five 

 times their normal frequency. As the blood is charged with 

 C0 2 a cyanosis of the mucous membranes appears. The lungs 

 are commonly congested and edematous so that rales are 

 heard on auscultation. In rare instances the respirations are 

 noisy or pronounced roaring occurs. As swallowing is diffi- 

 cult saliva, food or drugs may enter the windpipe, causing 

 foreign-body pneumonia and gangrene of the lungs. The 

 temperature is affected only in severe cases and usually just 

 before death or if some complication has set in (pneumonia, 

 septicemia). One or two days before death it may reach 

 110° F. As has been observed in other diseases accompanied 

 by severe muscular spasms the temperature remains high for 

 several hours after death (postmortem temperature). The 

 appetite usually remains good, although mastication is 

 labored. Food is often retained in the mouth or coughed out 

 into the manger. From a decomposition of the unswallowed 

 food and saliva the expirium becomes fetid. A regurgitation 



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