DISEASES OF THE NERVOUS 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 intestines.— (See “ Cramp colic,” p. 74.) 
Spasm of the neck of the bladder—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 diaphragm, 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 
36444°—16——15 
