For the direct cause of rachitis Glisson looked to the inequality of nutrition by the arterial blood, and for that of the curvature of the long bones to their superabundant vascularization. He found the disease mainly amongst the well-to-do classes, not unlike a modern American writer, who declares infantile paralysis to be the result of the nervousness of the better classes of the American people! John Mayow (1761) held a disturbance of the innervation responsible; Zeviani (in the same year), improper food in general, and particularly prolonged lactation; and Selle (1791), a peculiar diathesis (acrimonia rachitica). About that time a defective nutrition with abnormal function of the lymph-ducts was looked upon as the cause of rachitis by many--by others, an undue production of acid, and the softening of the osseous tissue thereby. This result was attributed by some to the influence of milk (Veirac, De Krzowitz). Attention was directed at an early time to phosphoric acid and lime, with the view that variations in the elimination of these substances might explain the occurrence of rachitis. A large quantity of both was found in some urines (Malfatti); a superabundance of phosphoric acid was presumed to prevail in the whole system (Wendt, Fourcroy); while symptoms resembling rachitis were found in animals fed upon small doses of phosphoric acid by Caspari (1824). Chossat fed young animals on food deprived of lime, and claimed to produce softening of the bones and death, a result which was denied by Friedleben. Guérin claimed to produce rachitis by feeding young animals on meat in place of their mother's milk, a result equally denied by Tripier, who, like Friedleben, found the bones under such circumstances more liable to fractures, but not rachitical. Wildt and Weiske found the bones uninfluenced by withholding lime from food; Forster, however, and Roloff claimed to notice a marked influence, and the latter {141} stated that animals, after having been rendered sick by depriving them of lime, recovered when they were again supplied with it. Wegner, in his numerous experiments with phosphorus, found that in growing animals it increases the growth and firmness of both long and flat bones; after the growth of the animal has been completed it renders epiphyses and vertebræ denser. There is no change, however, in the relative chemical composition of those parts. He found at the same time that results similar to those caused by the administration of phosphorus were obtained when food deprived of its phosphate of lime was given. But he met with no rachitical changes proper during these several procedures. Teissier having found an increase in the urine of rachitis after the administration of lactic acid, and lactic acid having been frequently found in the urine of rachitical patients by Ragsky, Morehead, Simon, and Lehmann, C. Heitzmann fed with lactic acid both carnivorous and herbivorous animals, found the cortical layer of