DEFINITION.--Rachitis is a general nutritive disorder, almost always of long duration, usually with an introductory stage of weeks or months and a course mostly extending over months or years. Its beginning is mostly gradual, its final recovery slow. It is complicated with or dependent on disorders of the digestive or respiratory apparatuses, which are preceded by a disposition probably created by an undue width of the arteries. It exhibits amongst its prominent symptoms muscular debility; perspiration; anomalies of the subcutaneous tissue, which is either very much infiltrated with fat or deprived of it; disturbances of the intellectual and moral functions, and of those of the large thoracic and abdominal viscera and lymphatic glands; changes in the latter may outlive all others. Its most perceptible symptom, however, consists in an inflammatory disease of the primordial cartilage of the epiphyses, a copious deposit in that region and also under the periosteum of the bones; curvature of the diaphyses, and, while absorption remains intact, softening and retarded ossification of the bone. Without these affections of the osseous system the diagnosis of rachitis is not complete. ETIOLOGY AND PATHOLOGY.--The nature of rachitis has been considered to be inflammatory by F. A. Walter.[2] Renard looked for that inflammation in the periosteum. Guérin emphasizes the vascular increase in periosteum, bone, and marrow; Trousseau and Lasègue the congestive character of the local tumefaction, besides fever and pain. Virchow also[3] inclines to the opinion that the rachitical process is of an inflammatory nature, though it be impossible to state the exact cause of the process. Still, he claims that we are no better off in regard to other inflammations of unknown character--for instance, those of the skin--and that we have to look for a future increase of our knowledge of such constitutional predisposition of the organism and of such specific qualities of the blood as will produce the local irritation of the osseous tissue in rachitis. Last, and mainly, it is Kassowitz who seeks the {138} essence of the rachitical process in a chronic inflammation originating in the points of apposition of the growing bones of the foetus or infant. During the chronic inflammation blood-vessels are formed in large numbers, and a morbid congestion takes place in all blood-vessels, but mainly in those of the localities in which new bone is forming; thus in the chondro-epiphyses, in the perichondrium and periosteum, and the sutural substances. Faulty introduction or elimination of lime has nothing to do with this process. It cannot be deposited in the current of a copious circulation; in fact, it is not deposited in the immediate neighborhood of blood-vessels to any extent. Even in otherwise normal bone hyperæmia produced by the experimenter softens the bone, which was fully formed before. If the relative percentage of lime were of any account in the