DISEASES OF THE NEEVOUS SYSTEM. 225 



appreciable symptoms during life. They are found in horses at all 

 ages, and are slow of development. They are found in one or both 

 of the lateral ventricles, enveloped in the folds of the choroid plexus. 



Melanotic tumors have been found in the brain and meninges in 

 the form of small, black nodules in gray horses, and in one instance 

 are believed to have induced the condition known as stringhalt. 



Fibrous tumors may develop within or from the meningeal struc- 

 tures of the brain. 



Gliomatous tumor is a variety of sarcoma very rarely found in the 

 structure of the cerebellum. 



Treatment for tumors of the brain is impossible. 



SPASMS, OR CRAMPS. 



Spasm is a marked symptom in many diseases of the brain and 

 of the spinal cord. Spasms may result from irritation of the motor 

 nerves as conductors, or may result from irritation of any part of 

 the sympathetic nervous system, and they usually indicate an ex- 

 cessive action of the reflex motor centers. Spasms may be induced 

 by various medicinal agents given in poisonous doses, or by effete 

 materials in the circulation, such as nux vomica or its alkaloid 

 strychnia, lead preparations, or an excess of the urea products in the 

 circulation, etc. Spasms may be divided into two classes: Tonic 

 spasm, when the cramp is continuous or results in persistent rigidity, 

 as in tetanus ; clonic spasm, when the cramping is of short duration, 

 or is alternated with relaxations. Spasms may affect involuntary as 

 well as the voluntary muscles, the muscles of the glottis, intestines, 

 and even the heart. They are always sudden in their development. 



Spasm of the glottis. — ^This is manifested by a strangling respira- 

 tion ; a wheezing noise is produced in the act of inspiration ; extreme 

 anxiety and suffering for want of air. The head is extended, the 

 body profusely perspiring ; pulse very rapid ; soon great exhaustion 

 becomes manifest; the mucous membranes become turgid and very 

 dark colored, and the animal thus may suffocate in a short time. 



Spasm of the intestinss. — (See " Cramp colic," p. 74.) 



Spasm of the neck of the hladder. — This may be due to spinal irri- 

 tation or a reflex from intestinal irritation, and is manifested by fre- 

 quent but ineffectual attempts to urinate. 



Spasm of the diaphragTro, or thumps. — Spasmodic contraction of 

 the diaphragm, the principal muscle used in respiration, is generally 

 occasioned by extreme and prolonged speeding on the race track or 

 road. The severe strain thus put upon this muscle finally induces 

 irritation of the nerves controlling it, and the contractions become 

 very forcible and violent, giving the jerking character known among 



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