Part 4

=Vice= in its various forms may become a genuine neurosis, the animal losing control of its actions.

=Violence= in the form of self-defence or aggression is seen in mares in heat, in bulls or stallions under sexual excitement, in animals roused by inconsiderate whipping, or in bulls looking on scarlet clothing.

Some high-spirited animals, under extreme fatigue from overwork, sometimes become violent but resume their docility under rest and food.

In all cases we must know the normal of an individual animal to enable us to properly appreciate any apparent deviation from the psychic norm. No less essential is it to take into account the environment and treatment of the patient.

With regard to localization of cerebral lesions, Sequin thinks emotions are probably generated in the basal ganglia such as those of the pons and thalami, while inhibition depends on the anterior cerebral cortical convolutions.

DIAGNOSIS, SYMPTOMS AND THEIR IMMEDIATE CAUSES. LOCALIZATION OF LESION IN SPECIAL SYMPTOMS.

Spasm, pain, numbness—irritation. Paresis, paralysis, anæsthesia (constant)—destructive lesions. Both combined—variable symptoms, recurrent. Definite, fixed symptoms—structural lesions, usually progressive. Symptoms, variable as to place, time, subsidence and recurrence—functional lesions. Brain lesions. Pressure on brain—pain, spasm, nausea, dullness, blindness, stupor, coma, palsy. Congestion and anæmia synchronous. Lesions of cortex. Encephalic lesions—hemiplegia, with spasms, increased reflexes, spasms follow cranial nerves, vertigo, apoplexy, epilepsy, dementia, coma, little muscular atrophy, or dermal sloughing. Spinal lesions, paraplegia without spasm, reflex reduced or nil, follow spinal nerves, head symptoms less, much muscular atrophy, bed sores. Sensory and motor tracts, in crus cerebri, respiratory centres—inspiratory expiratory, inhibition. Salivation, sneezing, coughing, sucking, chewing, swallowing, vomiting. Cardiac centres, accelerating and inhibitory. Vaso-motor centre. Spasm centre. Perspiratory centre. Pons. Corpora quadrigemini, crura cerebri. Thalamus, corpus striatum. Cerebellum. Cerebral cortex: in ass; in dog. Spinal lesions: lateral half section: central anteroposterior, vertical section: superior columns: inferior columns: cervical lateral columns: respiratory tract: glycogenic centre: pupillary dilator: cardiac accelerator; vaso-motor, sudoriparous: centre for anal sphincter: for vesical sphincter: genital centre: vaso-motor and trophic centres: muscular sense tract: superior column and Goll’s. Table of phenomena from cord lesions.

In =Irritation= of nervous organs the symptoms (spasm, pain, numbness) are usually intermittent.

In =Destructive Lesions= of nervous organs the symptoms (paresis, paralysis, anæsthesia) are usually constant.

When =irritation and destruction= are associated the symptoms are variable and frequent. The characteristic symptoms of the two may coexist or succeed each other.

=Structural Nervous Lesions= have symptoms that are definite in their area of distribution, nature (spasm, paralysis) and permanency. Objective Symptoms predominate and the case is likely to be progressive and fatal.

=Functional Nervous Diseases= have symptoms of indefinite distribution, variable in character, with intermissions and spontaneous disappearances (as under marked excitement) and subjective symptoms predominate. They may, however, last for a length of time without change.

Localisation of Brain Lesions.

Lesions of the cranial nerves and their superficial and deep centres of origin need not here occupy attention. These may be studied in works on anatomy and physiology. Attention may be drawn rather to the remoter effects of ganglia which affect or control distant action, and to general pressure on the encephalon.

=General Pressure on the Encephalon=, whether through fracture of the cranium and depression of bone, by acute congestion, by blood extravasation, by inflammatory exudation, or by acute abscess, will cause pain, spasms, nausea, dullness, blindness, stupor and coma. After expulsion of the cerebro-spinal fluid from the cranial cavity, the increasing pressure compresses the blood vessels, reduces or interrupts the circulation and abolishes the functions in the parts deprived of blood. Thus congestion of one portion of the encephalon is usually associated with diminished circulation in another portion. Disorder in the first may occur from hyperæmia and irritation and in another part from a consequent anæmia.

=Destructive Lesions of Cortex of One Cerebral Hemisphere= may or may not cause permanent symptoms, as shown by the passage of a crowbar through the front of the left hemisphere, yet the man survived for 13 years and showed no loss of intelligence, his disposition and character alone having changed for the worse. The one hemisphere may by itself sufficiently control mental acts, while the other lies dormant or may even have undergone degeneration.

=Diagnosis of Encephalic and Spinal Lesions.= The following may be taken as guiding principles:

=Encephalic=: Hemiplegic or bilaterally hemiplegic grouping of symptoms.

=Spinal=: Paraplegic grouping of symptoms.

=Encephalic=: Frequent contracture or spasms of paretic muscles.

=Spinal=: Paralysis more perfect and continuous.

=Encephalic=: Reflexes in affected muscles increased: Cerebral inhibition absent.

=Spinal=: Reflex abolished or reduced in parts the seat of the lesion.

=Encephalic=: Spasms in areas of distribution of cranial nerves (not spinal.)

=Spinal=: Spasms and paralysis follow distribution of spinal nerves.

=Encephalic=: Head symptoms frequent (vertigo, apoplexy, epilepsy, dementia, coma).

=Spinal=: Relative absence of head symptoms.

=Encephalic=: Comparative absence of marked muscle atrophy.