Abstract
An epidemic of nephritis occurred in our colony of albino rats (Mus norvegicus albinus), which during the past year had been fed a modification of the McCollum-Greenman cereal mixture, as follows: oatmeal, 1500 grams; cornmeal, 1500 grams; whole wheat flour, 1500 grams; flaxseed oil meal, 500 grams; bone meal, 75 grams; sodium chloride, 25 grams; dried milk powder, 250 grams. In addition, raw liver was fed weekly, and fresh cabbage twice a week. City water was supplied ad lib.
For a while, the rats seemed to thrive fairly well on this diet, although growth was somewhat retarded and reproduction subnormal. The presence of nephritis was discovered last December, during the course of some experiments on compensatory renal hypertrophy. The nephritis usually appeared chronic in form, though in some cases acute and fatal. Apparently all the rats in the colony were affected. The proportion of milk powder was doubled, fresh milk was added to the mixture, and cabbage fed thrice a week, but there was no improvement.
Sixty-five of the rats above 112 grams in body weight were killed, and the weights of the kidneys were compared with Donaldson's Wistar norm for corresponding body length. In 16 cases, the kidneys were above normal (maximum +63 per cent), and in 49 cases below normal (minimum —35 per cent). In spite of this variation in total kidney weight, the two kidneys of the same rat differed but little in weight. The left kidney weight was slightly less in 43 of the 65 cases, however, the general average being 4.6 per cent below the right (total range −18 to +13 per cent).
The kidneys frequently appeared light brown in color, occasionally slightly mottled. The surface sometimes appeared smooth, but often (especially in advanced cases) irregular, with numerous small gralnules and depressions.
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