DISEASES OF THE NERVOUS SYSTEM. 215 



of (liseast'd cerebral arteries and of tii)o[)lexy. The syinptonis are 

 drowsiness, vertigo, or attacks of giddiness, increased timidity, or 

 fear of familiar objects, paralysis of one limb, hemiplegia, imperfect 

 control of tlie limbs, and usually a weak, intermittent pulse. In some 

 cases the symptoms are analogous to those of apoplexy. The char- 

 acter of the symptoms depends upon the seat of the softening or 

 abscess within the brain. 



Cerebral sclerosis sometimes follows inllanmiation in the structure 

 of the brain affecting the connective tissues, which eventually become 

 hypertrophied and press upon nerve cells and iibers, causing their 

 ultimate disappearance, leaving the parts hard and indurated. This 

 condition gives rise to a progresssive paralysis and may extend along 

 a certain bundle of fil)ers into the spiiud cord. Complete paralysis 

 almost invariably supervenes and causes death. 



Lesions. — On making post-mortem examinations of horses wlii<li 

 have died in the first stages of either of these diseases we find an 

 excessive engorgement of the capillaries and small blood vessels, with 

 correspcmdingly increased redness and changes in both the contents 

 and the walls of the vessels. If death has occurred at a later period 

 of the disease, it will be found that, in addition to the redness and 

 engorgement, an exudation of the contents of the blood vessels into 

 the tissues and upon the surfaces of the infhimed parts has super- 

 vened. If the case has been one of encephalitis, there will usually 

 be found more or less watery fluid in the ventricles (natural cavities 

 in the brain), in the subarachnoid space, and a serous exudation be- 

 tween the convolutions and interstitial spaces of the gray matter un- 

 der the membranes of the brain. The quantity of fluid varies in 

 different cases. Exudations of a membranous character may l)e 

 present, and are found attached to the surfaces of the pia mater. 



In meningitis, especially in chronic cases, in addition to the serous 

 effusion, there are changes which may be regarded as characteristic in 

 the formation of a delicate and highly vascular layer or layers of 

 membrane or organized structure on tiie surface of the dura mater, 

 and also indications of hemorrhages in connection with the membra- 

 nous formations. Hematoma, or blood tumors, may be found em- 

 bedded in this membrane. In some cases the hemorrhages are copious, 

 causing paralysis or apoplexy, followed by speedy death. The menin- 

 gitis may l^e suppurative. In this case a puslike exudate is found 

 between the membranes covering the brain. 



In cerebritis, or inflammation of the interior of the brain, there 

 is a tendency to .softening and suppuration and the formation of 

 abscesses. In some cases the abscesses are small and numerous, sur- 

 rounded with a softened condition of the brain matter, and some- 

 times we may find one large abscess. In cases of recent development 



