50 & 100 Years Ago

50 Years Ago

The question of how cells estimate their location within the body is closely related to that of why cells of a developing organism become differentiated ... We are now investigating the mechanism involved ... using abdominal segments of the pupa Galleria mellonella. A previous investigation showed that the scale patterns in Galleria¹ ... are oriented by a concentration gradient of an unknown diffusible substance³. The substance seems to be produced at one margin of the segment and destroyed at the other⁴ ... To move the concentration gradient to some other part of the segment, pieces of skin were rotated in the larvae by 180° ... The concentration gradient, the existence of which is confirmed by these results, obviously has two functions: (1) to orientate the scales by its direction, (2) to supply the cells ... with necessary information about their distance from segment margins and to induce the corresponding cuticular structures.

From Nature 22 October 1966

100 Years Ago

The Psychology of Relaxation. By Prof. G. T. Patrick ... In the author's view ... forms of human behaviour are, at bottom, illustrative of a single principle. The activities and relations of civilised life imply the upbuilding and functioning of extremely complex mental mechanisms full of tensions, restraints, and inhibitions. To maintain these always in operation is an impossible task. From time to time, therefore, the complexes break up, and man falls back with relief into conduct expressive of simpler mental structures organised and consolidated in the far distant days of the race's childhood: he plays, he laughs, he swears, he fights.

From Nature 19 October 1916 ¹