Etiology. 935 



concerning tlie licking disease of cattle (q. v.), according to 

 wliicli any toxic substance present in meadow plants interferes 

 with the bone-formation, an action which cannot be prevented 

 by the addition of lime salts to the food. Stoeltzner considers 

 it probable that rachitis develops through a functional insuffi- 

 ciency of an organ which is analogous to the thyroid gland. 



The importance of infection as an etiological factor was 

 frequently assumed, but only through the investigations of 

 Morpurgos (1900, 1902) did this hypothesis gain a more solid 

 foundation. These results are supplemented by those of Moussu 

 (1903), and also Lienaux (1907) supposes that rickets has an 

 infectious origin. 



The experiments of Morpurgos were made on white rats which liad developed 

 osteomalacia and which belonged to a breed that had been raised in his inf-titution 

 for seven years. In the bones, cord, spleen and liver of the affected animals he 

 found Gram positive diplocoeci, the cultures of which, on subcutaneous injection 

 into healthy rats of the same breed, produced, according to the age of the animals, 

 symptoms of typical osteomalacia or of rachitis. In adult animals the period of 

 inoculation was 8 days, but often weeks and occasionally months, while young 

 rats inoculated immediately after birth did not become ill until they were two or 

 three months old. 



It must be mentioned that Plana (1889) already described an infectious 

 ral>bit rachitis and that he obtained positive results iu young rabbits, after inoc- 

 ulation with the microorganism which he had isolated. Later, however, he dis- 

 claimed the correctness of his observation because he failed later on to find the 

 supposed virus in the affected bones and because animals kept in the same place 

 alfo became ill without being inoculated. 



Moussu watched a little pig become ill which was kept and fed together with 

 one suffering from snuffles; another pig fell ill two and one-half months after 

 l)eing put in the stall of an affected pig, which had not been cleaned previously. 

 By suljcutaneous inoculation of the bone marrow taken from pigs in the initial 

 stage of the disease, he succeeded in producing a similar disease in pigs, goats 

 and later in rabbits. Lienaux also saw two healthy pigs become ill three and 

 live weeks after having been brought together with an affected pig of the same age. 



It is supposed that the lime salts in the ready formed 

 bone substance undergo solution owing to an excessive forma- 

 tion of lactic acid in the intestinal canal (Heitzmann) or in 

 the intermediary metabolism, or then under the influence of 

 an acid that develops in the bony substance itself and exerts 

 a local action (Vierordt). In the former case it is assumed 

 that the alkalinity of the blood is diminished and therefore the 

 calcium of the bones is dissolved, while in the supposed local 

 acidulation the fixation of the lime salts, which circulate in 

 the blood, is impeded while in addition to this the already formed 

 bone substance is decalcified. 



While according to Heitzmann animals acquired rachitis or osteomalacia 

 after feeding with excessive amounts of lactic acid, Siedamgrotzky and Hofmeister 

 found only an increased i)orosity of the bones, without rachitic changes, in young 

 kids which, in addition to the acid, received an appropriate amount of lime salts 

 with their food. 



Heitzmann 's results cannot be admitted as proof, because he limited the 

 supply of lime and because, moreover, other authors always got negative results 

 from "feeding lactic acid. Nor has it been possible to demonstrate the presence 

 of considerabV amounts of lactic acid in rachitic bones. In fact, A'irchow found 

 the reaction of fresh rachitic bones to be always alkaline. 



