There is another interesting consideration in regard to the effect of wide arteries on the relations between the blood and tissues. A great many more blood-cells are required to fill the arteries when wide than when narrow. Now, the formation of blood-cells is hindered by any disease of the digestive and blood-preparing organs, so that the tissues are liable to show the relative increase in the percentage of water, which is uniformly confirmed for rachitis by the biochemists.
The pulmonary artery of the healthy infant is larger than the aorta by not more than four millimeters. In the majority of cases of rachitis examined by Beneke this difference in size was very much more favorable to the pulmonary artery; it is abnormally large in rachitis. This anatomical fact is suggestive of the pathological processes so frequently found in the lungs and in the neighboring lymphatic and large abdominal glands. For, while the amount of blood introduced into the lungs through its wide artery is unusually large, particularly so in a chest which is contracted in consequence of the rachitical process in the bones, the exit from the lungs is relatively impeded. Not only, however, the narrowness of the chest is a cause of this disproportion. For even in rather normal chests the lungs of rachitical children are relatively small.
The liver of almost all rachitical children is large. In but one-half of the cases this enlargement is accompanied with a large heart. In pure cases of scrofula, on the contrary, Beneke found a small heart, rather narrow arteries, and usually a small liver, the size of the lungs offering but few anomalies.
The spleen also is large in the majority of cases. Its size is not dependent on the large size of the liver or the small size of the lungs. For these conditions are found in the majority of cases only, not in all of them, and the large spleen is not always found with a large liver and small lungs. The variability of the anatomical conditions permits of various degrees of combination; so that varying combinations of rachitis with other constitutional disorders may correspond with the different sizes of the principal organs. After all, as there is a great deal of independence of these organs, as to size, of each other, the conclusion is justified that those differences are not the result of the disease, but that they are congenital and stand in some causal relation with it.
The kidneys are large in the majority of cases, like the spleen and liver, while the lungs are small. This disproportion is apt to result in a hyperæmic condition of all the organs of the abdominal cavity, and especially of the kidneys. To what extent this undue amount of volume interferes with, or increases, renal secretion, it is difficult to say. The amount of urine secreted by rachitical children is about normal, though, as already stated, the percentage of lime in it is rather diminished, contrary to the opinions held formerly.
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 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 the bones softened and the medullary substance hyperæmic, and claimed to produce rachitis in the former and osteomalacia in the latter. Both of these assertions were denied by Tripier and Toussaint, who insist upon Heitzmann's having selected animals which have a peculiar disposition to suffer from rachitis. Again, Milne Edwards and Boussaingault found the bones softened when they withdrew both phosphoric acid and lime from the food, without restoring the bone's consistency by administering powdered bone. But, lately, Ad. Baginsky states that he produced rachitis by withholding lime, and increased the effect by introducing lactic acid. By so doing, however, he changed only the relation of the mineral to the organic substances, without interfering with the normal proportions to each other of the constituents of the ashes. Beneke, finding oxalic acid in the urine in many cases of rachitis, attributes to it the want of calcification in rachitis, and Senator suggests that what impedes the deposition of bone might be formic, acetic, and lactic acids, which are also found in the young osseous tissue.6
6 L. Fürth, Path u. Ther. d. Rachitis, Wiener Klinik, 1882.
Of these statements many are uniform, others contradictory. Thus far, they are not convincing except in one way—viz. that both withholding and introducing certain ingredients, mainly lime, influence the growth of the bone considerably. This may prove nothing else but that lime is of paramount importance in the building up of bone, and that bone in the period of rapid development is amenable to a great many influences.
It is in the period of rapid development that rachitis is observed. Thus it occurs in every stage of intra-uterine and infant life. It is met with in the foetus in very early intra-uterine life; it is found as a congenital affection, continuing to develop after birth when it has originated in the latter half of foetal existence; there is, thirdly, the rachitis of early infancy; and, lastly, that of advanced infancy and childhood. Of 624 cases of rachitis enumerated by A. Baginsky, there were 256 less than a year old, 313 in the second, and 63 in the third year. After this time rachitis is rare, as far as the active symptoms of the disease are concerned. But still, a retarded form of rachitis (r. tardiva) has been described by some authors. It is said to occur about puberty, and to exhibit local changes in the bones of genuine rachitical character, but to be wanting in all the other symptoms required for the diagnosis of general rachitis. Such cases have been described by C. Lucas.7 He found it complicated, now and then, with albuminuria. The occurrence of the latter at that time of life had been referred to by Moxon.8 The principal symptoms described by Lucas are scoliosis, talipes valgus, and genu valgum. The epiphyses were slightly thickened; there were pain in the limbs, languor, and pallor. In some of the cases there were also rachitical deformities dating from infancy. He believes rachitis of adolescence to exhibit more symptoms belonging to relaxation of the ligaments than to softening of the bones.
7 Lancet, June 9, 1883.