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Rh births for every two deaths. This evidence seems to answer our questions. The sharp check in the growth of negro population between 1910 and 1920 was due primarily to the flood of migration from the agricultural districts of the South largely to the cities and industrial districts of the North, but partly also to the cities of the South, and the exposure of negroes in their new homes to conditions tending to raise the death-rate or reduce the birth-rate, or both. The census of 1920 showed that about 19.9% of the negroes were living in states other than those in which they were born. But contrary to popular belief the proportion of those who had migrated from the South to the North and West was only about one-fourth larger than that of those who had migrated from the North and West to the South.

The white race is not equally burdened. In the cities of the registration area in 1915-9 there were only 62 deaths among whites for each 100 births, the corresponding figure for negroes being 121. In this regard the negroes of the United States are in somewhat the same position as the whites on both sides of the Atlantic a century or more ago, when cities were in a sense parasites upon the surrounding rural districts, at whose expense alone they could grow or even maintain themselves.
 * (W. F. W.)

 NÉNOT, PAUL HENRI (1853-), French architect, was born in Paris in 1853, and when only 13 years old, was placed in the studio of M. Lequeux as architectural pupil, coming there under the influence of J. L. Pascal. Thence, when 15, he went to the École des Beaux-Arts, breaking off his studies in 1870, immediately on the outbreak of war with Germany, to enlist in an artillery regiment. Here he gained, as his first distinction, the Military Medal, and at the conclusion of the war, it was with difficulty that his patriotic enthusiasm allowed him to reassume a non-military life. He continued, however, his course at the École des Beaux-Arts, and in 1877 gained the Grand Prix de Rome. During these years he was working in the office of C. Garnier of the Opera House, Paris, and after the winning of the Grand Prix he travelled for a considerable time in Italy, Greece and Egypt. While holding this prize in Rome, he competed for the Victor Emmanuel monument in that city, receiving for his design the premium of 50,000 francs, the work itself being entrusted to an Italian. On his return to France, he entered for the great competition for the rebuilding of the Sorbonne, in which he was successful, and in 1882, despite discussion as to entrusting to so young a man such an important commission, he commenced in 1885 a work that was to occupy him for the next 17 years. He did not, however, undertake it till after a prolonged tour of inspection of the universities of Germany, Austria, Holland and Belgium. The building forms a huge parallelogram of over 900 ft. in length by 325 ft. in width, and its plan is brilliantly conceived, taking as its dictating condition the retention of Richelieu's chapel of the Sorbonne. Throughout the whole of his consideration of the treatment of this, as indeed of his other buildings, Nénot relied steadfastly on the assistance of the sculptor and the painter, and the grand amphitheatre gave him the opportunity he absolutely insisted on of employing for its decoration Puvis de Chavannes, whose mural painting of the “Sacred Grove” is his masterpiece. The hall itself, used as a salle des conferences, is an admirable example of the D-plan carried by a series of alcove recesses to an ultimate development. Nénot's other work gives evidence in equal manner of the tradition he carried forward from the school of which half a century before, Duc, Labrouste and Dubon were the founders and upholders, and shows a similar tendency to breathe fresh and revitalizing inspiration into the vernacular architecture of France. His other buildings, mostly in Paris, include the Institut Océanographique, the offices of the Compagnie Générale and those of the Compagnie Nationale des Wagons-Lits. He received many distinctions, becoming a member of the Institut in 1895, and being later elected president of the Société des Artistes Français. He was awarded the gold medal of the Royal Institute of British Architects in 1917.  NERVOUS SYSTEM. The purpose of this article is to give a general view of the scope and limitations of surgery

as applied to injury and disease of the nervous system. It is essentially concerned therefore with the principles of modern surgical neurology rather than with clinical, pathological or technical details.

The nervous system (see ) is unique among the various systems into which the body is conventionally divided by the descriptive anatomist in being everywhere sharply marked off by definite anatomical and physiological boundaries from all the other tissues. It is a system in the strictest sense of the term. Its substance is elaborately insulated from contact with non-neural tissues except at the minutely limited points where contact is necessary for function, and correspondingly its pathology comprises principles which are characteristic and peculiar to it. In the mechanisms of injury or disease, in the processes of recovery and repair and in the response to the action of drugs the nervous system displays qualities which are special to it and not to be found elsewhere. It is natural therefore that the general principles of surgery need to be qualified in certain ways before they can be applied satisfactorily to surgical neurology.

The three great divisions of the nervous system brain, spinal cord and peripheral nerves coincide nearly enough with differences of surgical principle to allow the surgery of them to be dealt with under corresponding heads.

Surgery of the Brain.—The brain differs from all other organs of the body in being enclosed in a capsule of bone, and in a capsule therefore which is incapable of being stretched by any physiological force. The normal response of other organs to injury or disease is swelling, and this possibility of the occurrence of swelling allows of the presence of inflammatory products, of extravasated blood or oedema fluid without the circulation of blood through the organ being grossly impeded. In the case of the brain swelling the result of injury or disease is strictly limited by the skull, with the result that products of inflammation (or extravasated blood) or oedema fluid press on the vessels of the brain—veins, venules and capillaries according to the amount of exudation—and limit the circulation through them. The consequence is that any intracranial lesion other than a purely degenerative one is always accompanied by more or less wide-spread circulatory disturbances in the brain.

Now the functional activity of the brain is immediately dependent on blood supply, so that a cerebral lesion, as it necessarily interferes with blood supply, must always produce disturbances of function by this mechanism. In the case therefore of a given lesion such as a tumour or a haemorrhage the symptoms will be produced in two ways. First there will be symptoms due to loss of the function of the piece of brain occupied and destroyed by the tumor or haemorrhage, and secondly there will be symptoms due to disturbance of function in the surrounding region of brain where the circulation is impeded by pressure.

This dual causation of symptoms is a fundamental principle in cerebral pathology, and there are two corollaries of it of equal importance. In the first place the loss of function due to circulatory disturbance may be and frequently is as complete as if it were due to actual destruction of the brain substance; and in the second place the symptoms due to circulatory disturbance are in the majority of cases more conspicuous and more important than those due to the directly destructive effect of the lesion. It follows from these considerations that in many cases in which surgery is unable to deal curatively with the actual diseases itself it can produce benefit by dealing with secondary circulatory disturbance through the relief of pressure. Since the secondary pressure effects of many cerebral tumours are extremely distressing (severe headache, persistent vomiting and failure of vision), the merely palliative relief of abnormal intracranial tension is an important function of cerebral surgery.

While disturbance of function due to circulatory embarrassment can be got rid of if the abnormal intracranial tension can be completely relieved, loss of function due to destruction of the brain substance is permanent. There is no such thing as regeneration of the brain tissue, or the taking over of the actual function of a destroyed part by another part, and surgery can do nothing to restore a piece of brain that has been destroyed. 