Abstract
The work described in this paper is presented with the view of re-emphasizing the importance of the use of false screen bottomed cages in vitamin studies when rats are used as the experimental animals. Steenbock, Sell and Nelson 1 have pointed out that rats which do not have access to their own feces require a larger proportion of vitamin B in the basal ration than those rats which ingest variable amounts of excretory material daily. In our studies of vitamin B in the past (using diets deficient in this vitamin), we have often been unable to account for the lack of uniformity in the development of animals from the same litters on identical diets. In fact certain animals grew satisfactorily for many weeks on a vitamin B deficient ration. In watching the animals over relatively long periods it was observed that those animals whose food intakes and growth curves were most satisfactory were in the habit of ingesting relatively large amounts of excretory material; for example we have noted a few animals which would consume as many as 15 to 20 pieces of feces in the space of eight or ten hours.
In order to study the matter more thoroughly 63 rats were placed on experiment in individual cages. All animals received a basal ration consisting of casein 18, salts 3, agar 2, dextrin 77 and 5 drops of cod liver oil daily. Iodine was furnished in the drinking water. A number of the animals were placed in cages without screens while the remainder were distributed in cages containing false bottoms made of galvanized wire screens (3 meshes to the inch). The false bottoms were constructed about 1 1/4 inches above the cage pans in order that the particles of feces would fall through the screens to the pans below where the rats could not reach them.
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