Note on the weight of the adrenals in crosses between the albino and the wild Norway rat (Mus norvegicus.)

Abstract

When the weight of the adrenal glands is compared with either the body weight or the body length, the wild pigmented rat is found to have much heavier glands than the domesticated albino. The females in both groups have heavier glands than the males, but the difference in weight between the glands of the two sexes is less in the wild gray form. 1

The following experiments were undertaken to determine the weight of the adrenals in descendants from albino by Norway ancestors. It was appreciated that these observations must necessarily be made under the conditions of domestication and that the effect of domestication must be considered in the interpretation of the results. Under these limitations the purpose was to observe in what way the weight of the adrenals was related to pigmentation.

A wild gray male was crossed with a stock albino female and the offspring used for this work. The weights of the adrenals in the original pair are, unfortunately, not available. The values found in the other wild gray rats captured in the same vicinity are, however, close to those given by Hatai. 1 In our colony the average values for the female albino adrenals vary less than one per cent from that given in Table 71, “The Rat”. 2 One hundred and two animals were examined, covering four generations. Twenty-two of these, however, had pus in the ears or showed gross pathological changes in the viscera, usually the lungs. Since disease seems to influence the size of the adrenal glands, these animals were excluded and the eighty remaining animals were used in the computation.