DISEASES OF THE BEAIN. 195 



acute encephalitis, and is due to softening of the brain or to exuda- 

 tion into the cavities of the brain or arachnoid space. 



Softening and abscess of the brain is one of the terminations of 

 cerebritis. It may also be due to an insufficient supply of blood as a 

 result of diseased cerebral arteries and of apoplexy. The symptoms 

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

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

 control of the 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 ux^on the seat of the softening or 

 abscess within the brain. 



Cerebral sclerosis sometimes follows inflammation in the struct- 

 ure of the brain affecting the connective tissues, which eventually 

 become hypertrophied and press ujDon nerve cells and fibers, causing 

 their ultimate disappearance, leaving the parts hard and indurated. 

 This condition gives rise to a progressive paralysis and may extend 

 along a certain bundle of fibers into the spinal cord. Complete 

 paralysis almost invariably supervenes and causes death. 



Lesions. — On making post-mortem examinations of horses which 

 have died in the first stages of either of these diseases w^e will find an 

 excessive engorgement of the capillaries and small blood vessels, with 

 correspondingly 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 en- 

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

 tissues and upon the surfaces of the inflamed parts has supervened. 

 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 between the 

 convolutions and interstitial spaces of the gray matter under the 

 membranes of the brain. The amount of fluid varies in different 

 cases. Exudations of a membranous character may be present and 

 are found attached to the surface 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 la3'^ers of 

 membrane or organized structure on the 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 apoplexj^, followed by speedy death. The menin- 

 gitis may be 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 



