100 YEARS AGO

The theory of the origin of sleep which has gained the widest credence is the one that attributes it to anaemia of the brain. ⃛ It has been supposed, but without sufficient evidence to justify the supposition, that this anaemia of the brain is the cause and not the sequence of sleep. The idea behind this supposition has been that, as the day draws to an end, the circulatory mechanism becomes fatigued, the vasomotor centre exhausted, the tone of the blood vessels deficient, and the energy of the heart diminished, and thus is the circulation to the cerebral arteries lessened. ⃛ The alternative theories, which have been suggested to account for the onset of sleep, may be classed as chemical and histological. ⃛ It is held possible that the dendrites or branching processes of nerve cells are contractile, and that they, by pulling themselves apart, break the association pathways which are formed by the interlacing or synapses of the dendrites in the brain. Ramón y Cajal, on the other hand, believes that the neuroglia cells are contractile, and may expand so as to interpose their branches as insulating material between the synapses formed by the dendrites of nerve cells.

From Nature 5 May 1898.

50 YEARS AGO

As I look at a living organism, I see reminders of many questions that need to be answered. Not all these questions are obviously important, nor would their answers be useful — but we want them answered. Thomas Wright in 1601 said, “Nothing is so curious and thirsty after knowledge of dark and obscure matters as the nature of man” — of scientific men especially, he might have said. What is skin, fingernail? How do fingernails grow? How do I feel things? How are nerves built and how do they function? How do I see things? ⃛ The basic answers to all these questions are not to be found in books. Even though Chaucer said

For out of olde feldes, as men seith,

Cometh al this newe corn fro yeer to yere;

And out of old bokes, in good feith,

Cometh al this newe science that men lere,

he was before long corrected by Francis Bacon: “Books must follow sciences, and not sciences books”. — Linus Pauling

From Nature 8 May 1948.