disturbance of the whole of it, and therefore complete hemiplegia. But even in these cases the earliest signs of injury usually point clearly to a more definite localisation. Hence the importance of watching constantly a case of head-injury.

Conjugate deviation of the eyes and turning the head to the opposite side, with elevation of the eyelids and dilatation of the pupils, point to irritation of the base of the first frontal and neighbouring part of the second frontal convolution (12).

The leg-centre is situated about the upper extremity of the fissure of Rolando (2).

In exceptional cases, local and general spinal paralyses may result from the effect on the spinal cord or medulla oblongata of sudden displacement of cerebro-spinal fluid due to blows on the head.

Areas 4, 5, and 6 are centres for movements of the arm.

Areas a, b, c, and d are associated with movements of the wrist and fingers. Note their proximity to the facial and oral centres (7 to 11). Brachial monoplegia is less frequent than brachiofacial paralysis. 4 is the centre for adduction and retraction of the arm, 5 for forward extension, 6 for supination and flexion. It will be noticed that these and the other arm centres lie in the ascending parietal and upper part of the ascending frontal convolutions.

Combined arm and facial paralysis, often associated with aphasia if the right arm be affected, results from lesions of the middle or lower third of the ascending convolutions (about 7, 8, 11).

Aphasia points to injury of the posterior part of the inferior frontal convolution and lower end of the ascending frontal (9, 10).

To show the relations of individual convolutions and fissures to the skull and its sutures.

Diagnosis of Cortical Paralysis.-Apart from the consideration of the cause, &c., there are no features distinguishing hemiplegia due to general destruction of the motor area of the cortex from hemiplegia due to destructive lesions of the corpus striatum. In each case those movements are most paralysed which are most volitional. Sensation is not affected if the lesion be strictly limited to the cortex or to the anterior twothirds of the internal capsule. The nutrition or electric contractility of the paralysed muscles is not directly impaired. There is a tendency to the development of descending sclerosis of the motor tracts of the crus, pons, medulla, and spinal cord, and the appearance of late rigidity or contracture of the paralysed limbs.

There is said to be less difference in the temperature of the two sides of the body when the hemiplegia depends on cortical than when it is the result of central disease.

Hemiplegia, however, is not the most common type of the former, but more frequently a succession of dissociated paralyses or monoplegia. A monoplegia advancing progressively towards a hemiplegia is very significant of cortical disease. Monoplegia is very frequently associated with monospasm or early rigidity of the paralysed limb, or of the muscles governed by the centres surrounding the lesion. Cortical paralyses are frequently erratic and transitory. Early rigidity, so frequent with cortical lesions, is rare in central cerebral disease. Consciousness is comparatively less frequently lost in cases of sudden cortical lesion. There is frequently localised pain in the head.

Irritative Lesions of the Motor Area. These are such as cause convulsions. Unilateral convulsions do not necessarily signify irritation of the motor area. Long-continued irritation of any other part of the hemisphere may cause them. But monospasms and convulsions which begin invariably in the same way and do not cause loss of consciousness, and which are followed by paralysis more or less permanent, indicate an irritative lesion of the motor area.

An irritative, as compared with a destructive lesion, can only be localised approximately. An irritative lesion of one centre may discharge' neighbouring centres. Hence the

march' of the spasm should be minutely investigated in each case, the first convulsion in a given attack possibly indicating the exact cerebral locality.

Lesions of the Sensory Regions.-Complete unilateral hemianesthesia (affecting all the organs of sense of the corresponding side) points to lesion of the posterior part of the internal capsule (of the opposite side). As regards vision in these cases, the eye is rarely quite blind. There is rather a condition of ambly. opia and a remarkable contraction of the field of vision.

Bilateral hemiopia may mean a lesion of one optic tract or of the corpora geniculata or the posterior part of the optic thalamus, and several cases have been reported of late in which abscesses affecting the medullary fibres of the posterior lobes. have been associated with hemiopia. Lesions of the occipital lobes are often latent; but the occipito-angular region is the visual centre, though there is yet some dispute as to the exact relations to vision of the angular gyrus and occipital lobe respectively.

The angular gyrus is marked (13, 13').

The auditory centre is in the superior temporo-sphenoidal convolution (14).

The olfactory centre lies in the lower extremity of the temporo-sphenoidal lobe. 'Destruction causes no motor paralysis, but is followed by loss of smell on the same side; and, when the lesions invade not merely the subiculum (cornu Ammonis) but the neighbouring regions on one side, taste also is affected on the opposite side of the tongue.'

Tactile sensation is probably located in the region of the hippocampus and uncinate gyrus.

It is to be borne in mind how easily sensory defects are overlooked unless carefully searched for.

Cortical lesions do not seem to cause deafness or blindness in the sense of 'actual insensibility to optical or auditory stimuli of a complete or enduring character,' but rather subjec tive deafness and blindness, or abolition of visual or auditory perception or discrimination.' The conditions have been called by Kussmaul, 'word-blindness' and 'word-deafness.' The

former means inability to translate written symbols into ideas; the latter, to understand spoken words.

It is important to note that, corresponding sensory centres on the right and left sides of the brain being not always symmetrically developed, the effects of injury may vary greatly with the side affected.

Lesions of the Occipital Lobes.-These are often latent. It has, however, been stated that they cause a tendency to acute sloughing over the sacrum. Occasionally there occur cutaneous formication and similar subjective sensations. It is probable that mental disturbances are somewhat frequently associated with the lesions under consideration.

According to Charcot, the cortical centres are not distinctly defined and differentiated in infancy.

Upon the whole of this subject, refer to Ferrier on 'The Localisation of Cerebral Disease.'

Heart, Injuries of. See INJURIES OF CHEST.

Hernia. This word, which probably is derived from the Greek ernos, a shoot, is applied to the projection of a viscus through the wall of any of the body-cavities, e.g., hernia cerebri, hernia of lung; and, by extension, it is given even to such phenomena as bulging of tunica intima of an artery through an opening in the media and adventitia. But 'hernia' used without qualification refers only to hernia abdominalis. Causes.-Predisposing: 1, Sex, four times as often in males as in females. 2, Age, most hernias develop before age of 35. 3, Occupation, habit of making violent efforts. 4, Hereditary conformation, including patent tunica vaginalis funiculi, abnormal laxity of mesentery, congenital defects of abdominal walls. 5, General weakness of the system. 6, Excessive obesity and flabbiness. 7, Pregnancy. 8, Defects in abdominal wall of traumatic origin, cicatrices, &c. Observe that number 4 includes 3 causes. Cause 6 acts strongly if obesity rapidly diminishes. Exciting causes.- Sometimes a strain or violent efforts often repeated. Cough. In male infants, the application of a truss to an umbilical hernia may result in the production of an inguinal hernia. Symptoms.-In earliest

1 I feel inclined to doubt this, as I find that in most cases of combined umbilical and inguinal herniæ, the latter has appeared before any appliance has been placed on the former.