In 1917 Chick and Hume, of the Lister Institute, extended the observations of Hoist and his co-workers by making a comparative study of the values of a number of food-stuffs as protectives against scurvy (19). There are two methods which may be employed for the study of such a problem. One is to employ animals of a definite and uniform size and add to a scorbutic diet a certain amount of the food under examination to discover whether or not the animals are protected from the disease. The alternative is to produce first the condition and then attempt to relieve the animals by the administration of the food, the anti-scorbutic properties of which are under investigation. Chick and Hume adopted the preventive type of experiment. They fed their animals oats and bran, which they found would in about three weeks produce scurvy in a guinea pig weighing about 280 grams. The substance to be studied was added in known amount and the duration of the protection, if any, observed.

Chick and Hume emphasized the superiority of this method over the curative type. In the latter the animals return to normal slowly even when the anti-scorbutic potency of the diet is made high, and their improvement is less well marked when it is low. This method leads to confusion in interpretation of results.

As the outcome of their studies Chick and Hume constructed a table (see page 181) in which the protective values of a number of foods are compared. For comparison they likewise included such data as is available to indicate the content of each of the foods in the anti-beri-beri dietary factor (water-soluble B). The latter information was gained by tests of the curative type on pigeons in which polyneuritis was developed by restriction to a diet of polished rice.

In a later paper, Chick, Hume and Skelton (20) discussed their experimental work in relation to the views which had been expressed by the several investigators, who held that scurvy was not a deficiency disease in the same sense as beri-beri or polyneuritis. In the light of their data the erroneous conclusions of McCollum and Pitz were explained. It was shown that the anti- scorbutic value of milk had been greatly over-rated. Chick and her co-workers adopted hand feeding, instead of allowing the guinea pigs to eat of milk ad libitum, and showed that when less than 50 c.c. of raw milk daily supplemented a diet of oats and bran it did not defer death from scurvy beyond thirty days or thereabouts. When 50 c.c. of raw milk were actually consumed daily the life of the animals was extended to about seventy-five days. An intake of 100 to 150 c.c. of milk daily served to maintain the animals in a state of health during a period of sixteen weeks, at which time the observations were discontinued.