THE ETIOLOGY OF RICKETS: AN EXPERIMENTAL INVESTIGATION
BMJ (Clinical Research Edition)
These last experiments slhowed that while all the. pups of two litters kept in the laboratory upon an abundant supply of wlhole milk and oatmeal porridge developed rickets, two pups from each of the litters kept in the country on skimmed milk and oatmeal remained free of the disease. The present series of observationsshows that pups kwept in the laboratory develop rickets even on an abundant supply of milk fat (as much as 7.5 or even 11 grams per kilo) and oatmeal porridge, but that those on
... ut that those on the same amount of separated milk (0.2 to 0.7 gram of milk fat) and porridge develop the disease more rapidly. The energy value of the separated milk diet was necessarily lower than that of the full milk diet (207 to 267 calories as'against 270 to 437 calories), and hence it is possible, as is suggested by the observations on infants by Hess and Unger,' that a low energy intake may predispose to the disease, altliough it is not a causal factor. To test this the next experiment was arranged so that pups of three litters, whichl were available at the time, should have the diet increased proportionately to their increase in weight, and tllat tlle eneray intake should be kept ample tlhroughout the period of growth, but tlhat, wlhile one series of pups should have the energy supplied largely from whole milk-freshi and dried-with bread, anotlher should have it from dried separated milk and bread, another from lard, which tlle Vitamin Committee5 of the Medical Research Council class as a fat free of their anti-rachitic vitamin, anad the last series from dried separated milk and bread. Scrupulous care as to cleanliness was observed tllroughout this experiment. The result was that all the pups, with one exception, reached fifteen to eiglhteen weeks free of rickets, although those upon tlle separated milk and bread diet had only 0.3 to 0.6 gram of milk fat per kilogram per day. The basis of Mellanby'st6 experimental work is that separated milk up to 250 to 350 c.cm. and white bread, even with linseed oil, yeast, and orange juice, will not prevent the onset of rickets in pups between six and twelve weeks of age, while whole milk will prevent it, and upon thjis is based the practica1 recommendation of the Vitamin Committee,5 p. 99, that full cream milk should be used by children for the prevention of the disease. Butter is placed with cod-liver oil (p. 102) as the substance richest in "fat-soluble A or anti-rachitic factor," but bothl of tlje two pups in our series to which butter was administered in large quantities developed rickets, while its administration failed to cure or to prevent the advanlce of the disease in another. Our experience indicates that by attention to strict cleanliness it is possible to rear pups free from rickets in a laboratory. It is easy to rear them in the open air, even on a diet poor in milk fat. The work of Morpurgo on white rats, and the study of an epidemic of rickets among foxhounds in Adelaide by Bull,7 taken along with our results, point to tlle probability tllat a bacterial infection of the same non-specific character as that which the investigations of McCarrison lhave shown to be the causal factor in goitre, plays an important part in the etiology of the disease. A point of considerable interest demonstrated in our observations is thle more rapid growvthl of thle pup.s k;ept in thle open air.