Scientific Serials

Abstract

Bulletin de l'Académie Royale de Belgique.—Stas's determinations of atomic weights, by E. Vogel. In spite of Stas's conclusion that the atomic weights of the elements have no common measure, Prout's hypothesis has recently been regaining ground. Hinrichs's experiments have thrown doubt upon Stas's atomic weight determinations; and the suppositions made by Stas himself place it beyond doubt that all his atomic weights without exception are inaccurate. The cause of the great discrepancies in the values found by Stas himself lies in the variation of the weights of the substances taken. When to a solution of an alkaline chloride is added nitrate of silver to slight excess, a precipitate will be formed on adding more chloride. But experiment shows that a precipitate is also formed on. adding more nitrate, up to a certain limit which Mulder termed the limit of silver, as distinguished from the limit of salt for the addition of the chloride. The author shows that the true atomic weight cannot be derived from the mean between these two limits, and proves from Stas's own data that they may be equally well interpreted for entire as for fractional multiples of the atomic weight of hydrogen.—Chronometric determinations relating to the regeneration of nerves, by C. Vanlair. The experiments, conducted by the physiological method, were made upon a motor nerve, the facial, a nerve whose simultaneous bilateral section is inconsistent with life, the pneumogastric, and a mixed sensory nerve, the sciatic. The right facial nerve of an adult rabbit, the two inferior branches of which were cut as they emerged from the parotid, required eight months for their regeneration. The right pneumogastric of an adult dog was cut in June 1889, and the left, one year afterwards. In August, 1891, the right nerve was cut again, but, after some initial troubles, the dog's health remained perfect throughout. Since the simultaneous section of the two branches is invariably fatal, it follows that during the time intervening between the sections the branch last cut must have reunited. This gives a velocity of reproduction of 3 c.m. per month, or 1. mm. per day. In the dog, and doubtless also in man, nervous regeneration, undisturbed by any accidental obstacle, takes place with an almost perfect chronological regularity. The average time necessary for initial proliferation is about forty days. For a section of about 1 c.m. length, the development of the new fibres takes place at a rate of 0.25 mm per day. The speed is greater at 2 c.m. but decreases again for greater lengths in proportion to such lengths.