ulcers, bullæ, defective growth of the nails, brittleness of the bones. Felons are common. There is loss of control over the bladder and rectum if the lumbar region of the cord be involved.

The prognosis is bad, although the disease extends over years. The latter stages of the disease resemble chronic muscular atrophy. Death may result from involvement of the medulla.

Treatment is inoperative. Arsenic and nitrate of silver are generally given as a routine, but beneficial results are not to be expected from medication.

COMPRESSION-MYELITIS (SLOW COMPRESSION OF THE CORD).

Etiology. The spinal cord may be compressed (a) by disease of the vertebral bones, especially caries; (b) by thickened membranes; (c) by tumors of the cord, membranes, or bones. The most common tumors are carcinoma, (usually secondary to primary growths in the breast), retroperitoneal sarcoma and aneurysm (causing erosion of the bodies of the vertebræ, so that they come to lie directly on the spinal cord itself), and sarcoma of the membranes.

The pathology is that of a pressure-atrophy.

The symptoms are those of chronic myelitis slowly developing with a prolonged stage of irritation.

Compression of the spinal-nerve-roots causes neuralgic pains with areas of anæsthesia (“anæsthesia dolorosa") and with muscular spasms followed by paralysis, loss of reflexes, and atrophy of muscle.

Compression on a spinal segment gives rise to anesthesia, paralysis, atrophy, loss of reflexes, and the reaction of degeneration in the muscles supplied directly from the compressed segment. Below the affected segment there are the symptoms of spastic paraplegia-paralysis, increased re

flexes, absence of atrophy and of the reaction of degeneration. There is loss of bladder- and rectum-control. If the compressed segment be in the lower dorsal and lumbar regions, the reflexes in the legs will be lost and the muscles will atrophy.

The prognosis depends upon the cause of the compression. Treatment is that of the original cause. Caries of the vertebræ is best treated by suspension. Tumors may be removed by operation if it be practicable. In some cases of bone disease laminectomy may be performed with benefit.

TUMORS OF THE SPINAL CORD.

Etiology and Pathology.-Tumors of the spinal cord are rare and are usually secondary to growths elsewhere. Sarcoma and tubercular, syphilitic, and gliomatous growths are most frequently observed. The compression of the spinal cord leads to a chronic myelitis at the seat of the growth, and in rare cases may induce the condition of syringomyelia.

Symptoms.-The symptoms are those of a compressionmyelitis or of Brown-Séquard's paralysis, of slow development and characterized by such extreme pain in the sensory areas corresponding to the segment in which the tumor grows that the name "paraplegia dolorosa" has frequently been applied.

The prognosis is bad in inoperable growths.

The treatment is to remove the tumor if possible; otherwise the treatment is symptomatic.

BROWN-SEQUARD'S PARALYSIS.

Etiology.-One half of the spinal cord may be destroyed by tumors, by hemorrhages, by disease of the vertebral bones, or by traumatism.

The pathology is that of a destructive lesion involving a lateral half of a spinal segment.

The symptoms are best appreciated by consulting the following table of Gowers:

Treatment is directed to the cause of the hemi-lesion; otherwise the treatment is that of myelitis.

5. DISEASES OF THE CRANIAL NERVES.

OLFACTORY NERVE.

Anosmia, or loss of the sense of smell, may occur with chronic nasal catarrh or with diseases of the olfactory nerves or bulbs following meningitis, frontal tumors, or caries of the bones. The symptom is not uncommon among insane and hysterical patients.

Hyperosmia, or increased sensitiveness, and parosmia, or subjective perversions, of the sense of smell, are not infrequently observed in neurotic patients. Parosmia may precede an attack of epilepsy.

OPTIC NERVE.

Many of the diseases of the optic nerve clearly belong to the domain of ophthalmology, and therefore will not be considered here.

Destructive lesions in various parts of the optic tract produce the following results (see Fig. 55):

1. Lesions of the optic nerve produce blindness of the corresponding eye.

2. Lesions of the chiasm may produce blindness of both eyes (if the chiasm be totally destroyed), temporal hemianopia (if the central part of the chiasm be involved), or nasal hemianopia (if both lateral regions of the chiasm be affected). 3. Lesions of the optic tract produce lateral hemianopia. 4. Lesions of the cuneus produce lateral hemianopia. 5. Lesions of the angular gyrus give rise to hemianopia and mind-blindness, rarely to crossed amblyopia.

Hemianopia, though usually of organic origin, may occur with hysteria, migraine, and lithæmia. In hemianopia, if the pupil reacts when a ray of light is thrown upon the sensitive half of the retina, the lesion is in the optic radiation or in the cerebral cortex.

THIRD NERVE.

Nuclear lesions of the third nerve are usually associated with disease of the other ocular-nerve-centres (see Ophthalmoplegia). Disease of the third-nerve-trunk is not uncommon. The nerve may be the seat of a neuritis (especially with locomotor ataxia and after diphtheria), it may be compressed by meningitis, tumors, or aneurysms at the base of the brain, or it may be paralyzed from exposure to cold, from rheumatism, from syphilis, or by an attack of migraine. Paralysis of the third nerve gives rise to external strabismus, ptosis, dilatation of the pupil, loss of pupil-reflex and of accommodation to distance, and to diplopia, or double vision.

A form of oculo-motor palsy is described as occurring chiefly in women, and as recurring at intervals of several months, associated with pain and migraine.

Spasm of the muscles supplied by the third nerve is not uncommon in meningitis and in hysteria. Slow rhythmical oscillations of both eyeballs (nystagmus) occur in congenital and acquired brain affections and in albinism, and is not uncommon among coal-miners.

FOURTH NERVE.

The causes of fourth-nerve-paralysis are similar to those causing third-nerve-palsy. The symptoms are a slight convergent strabismus when the eye is rolled downward, and double vision when the patient looks down.

FIFTH NERVE.

PARALYSIS.-The nucleus may be involved by hemorrhages or tumors of the pons, or the branches of the nerve may be affected within the cranium by meningitis, caries, or tumors. The lower divisions are not infrequently involved by tumors of the upper jaw. Primary neuritis is

rare.

Symptoms.-Sensory.-There is anæsthesia of the skin of the face and head, the conjunctiva, and the mucosa of the lips, tongue, soft and hard palate, and nose. The anæsthesia may be preceded by hyperæsthesia or by tingling feelings.

Motor. The temporal and masseter muscles are paralyzed, and the jaw, when depressed, moves toward the paralyzed side. The motor palsy is usually due to lesions involving the trunk of the nerves.

Trophic and Vaso-motor Changes.-There may be ulcerations of the mucosa, falling of the teeth, opacity and ulceration of the cornea, diminished salivary, nasal, buccal, and lachrymal secretions, flushings and pallor, and herpes. The trophic changes occur if the Gasserian ganglion is affected.