The use of raw milk was introduced by Jackson and Moore, and adopted by McCollum and Pitz and again by Pitz in a series of interesting experiments. The milk was given _ad libitum_. The results of these investigations were puzzling at first, until it was shown by Chick, Hume and Skelton that the dietary on which they were based contained a fundamental error which accounted for their lack of consistence. Although milk is not rich in the antiscorbutic factor, it possesses it in moderate degree, so that the outcome will be quite different according to whether a guinea-pig takes, for example, 50 c.c. or 100 c.c. daily. It is quite evident, therefore, that a food of this kind cannot be offered _ad libitum_, and that if this rule is not observed, most disconcerting results will follow.[36] This basic error in framing the dietary has made it impossible to accept the deductions of these authors. The conclusions of McCollum and Pitz are so striking and have led to such wide discussion, that they require consideration, in spite of the fact that the error in the dietary is now recognized. These authors found that the cæcum of their animals was greatly distended with putrefying fæces. As the cæcum is extraordinarily large and delicate in this species, they drew the deduction that the development of scurvy in the guinea-pig was due principally to the retention of fæces. "An impacted cæcum, the seat of putrefaction, may cause injury to the cæcal wall, sufficient to permit the invasion of the tissues by bacteria, or the animals may perhaps be injured primarily by the absorption of toxic products of bacterial origin." Accessory dietary factors or vitamines, according to this theory, are supposed to play no part in the disorder, and antiscorbutics, such as orange juice, are considered to owe their efficacy mainly to their laxative properties, and to be replaceable by other laxatives such as phenolphthalein or oleum petrolatum. The efficacy of orange juice is supposed to be due to its content of citrates, and to be replaceable by what was termed "artificial orange juice," a mixture composed of the various salts, citric acid and sucrose, in the proportions in which they are found in the natural juice.