100 YEARS AGO

It is interesting to note how the gradual discovery of the attendants of the various planets has influenced the compounding of the “laws” which from time to time have been found to approximately represent the positions of these bodies in the solar system. From the first discovery of Jupiter's four satellites by Galileo in 1610 to Huyghens, Cassini, and Sir W. Herschel, no regular relationship was perceived. When, however, in August 1877, Prof. Asaph Hall discovered the two moons of Mars, Deimos and Phobos ⃛ it was seen that all the then known satellites were grouped in a geometrical progression, reckoning outwards from the Earth. Thus the Earth had one, Mars two, Jupiter four and Saturn eight. This seeming regularity was broken by the discovery on September 9, 1892, of a fifth satellite to Jupiter ⃛ . This last discovery of a ninth satellite for Saturn will furnish a reason for a new series being formed, as counting from the Earth outward from the Sun, the numbers of satellites to the planets Earth, Mars, Jupiter and Saturn are now 1, 2, 5 and 9 respectively, and these numbers are very nearly proportional to the distances of those planets from the Sun.

From Nature23 March 1899.

50 YEARS AGO

Much of the published data regarding the mode of action of penicillin is necessarily concerned with secondary effects on bacteria, for example, rate of killing under different conditions, morphological changes, etc. By use of radioactive penicillin, it should be possible to find out directly something of the nature of the primary reaction between penicillin and the cell. Penicillin is taken up by all bacteria in amounts which increase with penicillin concentration ⃛ . There is, in fact, a direct correlation between the sensitivity of an organism and the amount of penicillin attached to it. ⃛ However, if growth is halted by cooling, or if the cells are already dead, there is still a rapid but smaller uptake. ⃛ Whatever the nature of the primary site of penicillin action, it is clear from this and other work that rapid growth exposes more centres in the bacteria with which the penicillin can react. The combination must either be by unusually strong adsorptive or by chemical forces.

From Nature26 March 1949.