50 Years ago

This article describes a model which imitates certain aspects of morphogenesis and maintenance in a developing embryo. The model consists of a number of artificial 'cells' (constructed from radio parts) which can stimulate and inhibit one another by means of connexions which are made through a switchboard. The pattern of activity generated, representing the growth pattern, was found to bear a remarkable resemblance to certain aspects of morphogenesis ... Many other properties of our system, with larger numbers of cells and with other ways of connecting them together, are reminiscent of the properties of growing embryos: for example, the patterns are in general homeostated — a disturbance producing only a temporary change in the pattern. Discrete differences (such as 'on' or 'off') appear between neighbouring cells, in contrast to the continuous differences which would be expected on a purely humoural mechanism of growth control.

Dr. R. J. Goldacre and A. D. Bean

From Nature 23 April 1960.

100 Years ago

In her letter to Nature on March 24 Miss I. Sollas remarks on the “canary-yellow” colour “in members of the stoat family when the winter whitening is incomplete,” adding, “there can thus be little doubt that the yellow body produced artificially in the fur of the albino rat is a substance similar to the yellow pigment of the stoat's winter coat ...” I do not know whether it has been recorded ... that a stoat's fur of the purest white will, after exposure to light in a museum case for a time, varying with the intensity of the light, invariably turn distinctly yellow — fainter, however, than “canary-yellow.” ... The usual reason assigned for the change is the absorption by the hairs of a small amount of fat out of the skin, induced by the light and heat of summer.

Henry O. Forbes

From Nature 21 April 1910.