In the brain the middle cerebral artery is affected most frequently.

Pathology. Varieties.-Aneurysms may be true or false. A true aneurysm is a circumscribed dilatation of one or more coats of an artery. A false aneurysm has for its wall the surrounding tissues, the blood-vessel having ruptured. Aneurysm may also be classified as regards its shape; when oval or spindle it is called fusiform, or cylindric aneurysm. When one portion of an artery is dilated into a pouch-like formation it is called a saccular aneurysm; when the blood finds its way between the coats of an artery, as a result of rupture of the inner coat (the middle coat may also be ruptured), it is called a dissecting aneurysm.

As has before been stated, the usual cause of aneurysm is arteriosclerosis. The blood-vessel loses its elasticity, the vessel becomes weakened, and any sudden strain may cause it to give way.

Miliary aneurysms are sometimes produced as a result of destruction of the outer coats of a vessel; for example, in a tuberculous lung, the process involving the larger bloodvessels. The outer coat becomes diseased and the inner protrudes, forming what is called miliary aneurysm. Again, an aneurysm may become very large, in some instances reaching an enormous size. The aneurysmal sac may contain laminated clots, often being healed. In very old aneurysms this clot may assume the appearance of being fibrous. In many aneurysms, however, no coagula are to be found. Atrophy, from pressure of surrounding tissues, commonly accompanies aneurysm. The vertebras, the ribs, and the sternum are not infrequently involved, and portions of these structures may entirely disappear. Pressure upon the bronchi may cause bronchiectasis, and pressure on the lung, atelectasis.

Rupture may result in the form of a slow leak or rapid gush. When the first portion of the arch of the aorta is involved the rupture may occur into the pericardium (see Hemopericardium). The rupture of the thoracic aorta may take place externally, into the pleural sac, mediastinum, bronchi, trachea, lungs, and esophagus. Rupture into the superior vena cava has been reported. External rupture is not uncommon.

Aneurysm of the abdominal aorta may cause atrophy of the vertebras and surrounding structures. Rupture may take place externally or into the peritoneal cavity. Aneurysms of the brain may be of quite large size or of the miliary character.

Hypertrophy of the heart, as a rule, occurs, being chiefly due to the arteriosclerosis which usually precedes the development of aneurysm.

Symptoms. The symptoms may be latent for a long period. The early diagnosis of aneurysm is often impossible, the symptoms being misleading. Among the earliest and most important symptoms is pain. It may occasionally be absent, but in the majority of cases it is the first, most important and enduring symptom. It differs greatly in continuity, variability, and character. It may be slight, or, on the other hand, severe enough to threaten life, or disturb the comfort and rest of the person affected. It is usually acute and paroxysmal, subject to remissions and exacerbations, or it may be dull, gnawing, and localized in the position in which the aneurysm occurs. Paroxysmal pain in some region in close relation to the aorta is always suggestive of aneurysm. The pain is often worse at night. In abdominal aneurysm the pain is likely to be severe and shoot through to the spine. It is intense and wearying in character, and rarely absent. The heart may remain entirely free from signs or symptoms for some time. However, in a number of cases palpitation

Occurs.

Important symptoms are pressure phenomena; thus, the pain may often be due to the aneurysmal sac pressing upon a nerve-trunk. Occasionally there is hyperesthesia and anesthesia. Hoarseness and aphonia may result from pressure upon the recurrent laryngeal nerve. Unilateral sweating and change in the size of the pupils are often symptoms of pressure upon the sympathetics. From pressure, particularly upon the left bronchus, tracheal tugging occurs. Pressure upon the pneumogastric may cause vomiting, and upon the esophagus may give rise to dysphagia. As a result of pressure upon the thoracic duct there may be extreme emaciation. Pressure upon the bronchus may result in dyspnea, which may be paroxysmal in character.

Cough and hemoptysis are frequent symptoms in aneurysm of the aorta. Pressure upon the superior vena cava may give rise to distention of the veins of the neck and face, causing cyanosis with edema. Pressure upon the inferior vena cava gives rise to similar conditions of the limbs and congestion of the viscera.

Changes in the pulse may occur, especially if the aneurysm is situated in the ascending part of the aorta; the pulse, com

pared with the apex-beat, is retarded. In the ascending aorta the carotid pulse may also be delayed. The location of the aneurysm may cause a delayed pulse of one side; for example, the left carotid and subclavian pulse may follow those of the right side.

Physical Signs of Thoracic Aneurysm. Inspection.— If the aneurysm have eroded the ribs or sternum, protruding itself externally, a pulsating tumor is seen, often producing a blue or livid discoloration of the skin.

Palpation. Palpation may show a downward displacement in the apex-beat of the heart, due to pressure from above downward and to the left, without signs of marked hypertrophy. The aneurysm, if palpable, reveals an expansile pulsating tumor, and a more or less distinct thrill, which is systolic in time. Tracheal tugging may also be noticed upon palpation. A distinct diastolic shock may sometimes be present over the base of the heart.

Percussion.-Percussion elicits flatness over the tumor. Auscultation.-Auscultation gives a distinct systolic bruit from the rush of blood through the distended tumor.

Signs of Rupture.-Rupture of an aneurysm is recognized by the instant collapse of the tumor, and symptoms of profuse and rapid hemorrhage.

Diagnosis. The diagnosis depends upon the recognition of the etiologic factor; the symptoms of pain, palpitation, and dyspnea, presence of tumor, with expansile pulsation, thrill, and bruit, and often dislocation of the apex-beat of the heart, accompanied by pressure phenomena.

Prognosis. The prognosis is always grave, although cure may take place.

Treatment.-Absolute rest in bed is of the utmost import

ance.

A diet in which fluids are largely eliminated (Tufnell treatment) is of use in some cases. The symptomatic treatment consists in the administration of large doses of iodid of potassium. The use of opium for the relief of pain should be delayed as long as possible.

Surgical Treatment.-The surgical treatment may consist in ligation, filipuncture, needling, electropuncture, compression and wiring, wiring with electrolysis, and the hypodermic use of gelatin.

ANEURYSM OF THE ABDOMINAL AORTA.

Etiology. The same causes which give rise to aneurysm of the thoracic aorta produce aneurysm of the abdominal aorta. The pressure symptoms relate more to the abdominal viscera and the lower extremity. The pain is constant, gnawing, shooting through to the back, and may radiate down the legs. The physical signs are the same as those in thoracic aneurysm, although the tumor is not nearly so likely to make its appearance.

Diagnosis.-Occasionally, masses of various kinds, such as tumors of the left lobe of the liver, of the stomach, or of the pancreas, or large glands, may give rise to some of the physical signs of aneurysm. However, the expansile pulsation is absent, although this is sometimes difficult to determine. If, then, the patient be placed in the knee-elbow position, and if the tumor falls forward, the signs of aneurysm will disappear. Prognosis. The prognosis is practically the same as that of thoracic aneurysm.

Treatment.-The treatment before described for thoracic aneurysm should also be adopted in cases of aneurysm of the abdominal aorta.

PART III.

DISEASES OF THE RESPIRATORY

SYSTEM.

DISEASES OF THE NOSE.

ACUTE RHINITIS.

Definition.-An acute catarrhal inflammation of the nasal mucous membrane, characterized by copious secretion of a serous or mucous character.

Synonyms.-Acute coryza; acute nasal catarrh.

Etiology. The affection is most often caused by cold and exposure, although it may result from trauma and the inhalation of irritants.

Pathology. In the first stage there is hyperemia and slight swelling of the mucous membrane and of the turbinated bones, accompanied by dryness of the membrane. This is followed by a profuse serous or mucoserous discharge, which later may become purulent.

Symptoms.-The attack may begin with slight chilliness and malaise, with some headache and pain referred to the nasal and frontal bones. The temperature is subfebrile, and the pulse is not altered. Stenosis of one or both nasal chambers may occur, due to the swelling of the mucous membrane of the nose. This is followed by profuse discharge of a mucous, serous, and finally seropurulent character. Sneezing is common, and the conjunctivæ may be injected. The discharge is sometimes acrid, and the lips and anterior parts of the nose may be slightly excoriated.

Complications.-The inflammatory process may invade the frontal sinus, the antrum of Highmore, the Eustachian tube, and the nasopharynx.

Prognosis.-Uncomplicated cases recover in from five to