Page:Popular Science Monthly Volume 15.djvu/293

 associate with those of our own time. The law of progress has been dominant among plants and animals, and not less upon the surface of the planet which they inhabit. It is the province of the biologist to trace the one series of changes, of the geologist to investigate the other. The geographer gathers from both the data which enable him to connect the present aspects of nature with those out of which they have arisen.

Storms and Neuralgia.—At the April meeting of the National Academy of Sciences, Dr. S. Weir Mitchell read a paper on "The Relation of Neuralgic Pain to Storms and the Earth's Magnetism." The interesting observations here recorded were made by Dr. Mitchell in conjunction with Captain Catlin, of the United States Army, who lost a leg during the war, and who, since that time, has suffered from traumatic neuralgia, sometimes in the heel, but more frequently in the toes, of the lost foot. The hourly observations cover a period of five years. For the first quarters of these five years there were 2,471 hours of pain; for the second quarters, 2,102 hours; for the third quarters, 2,056 hours; and for the last quarters, 2,221 hours. The greatest number of hours of pain is in January, February, and March; and the least in the third quarters, July, August, and September. During these five years, while the sun was south of the equator, there were 4,692 hours of pain, against 4,158 hours while it was north of the equator; and the greatest amount of pain was in the quarters beginning with the winter solstice, and the least was in those beginning with the summer solstice. The average duration of the attacks for the first quarters was 22 hours, and for the third quarters only 17·9 hours. By taking the four years ending January 1, 1879, it is found that, of the 537 storms charted by the Signal Bureau, 298 belong to the two winter quarters, against 289 for the summer quarters. Hence we have the ratio of the number of storms of the winter quarters and summer quarters corresponding to the ratio of the amounts of neuralgia for these respective periods, and the ratio of average duration of each attack for the same time corresponds closely with the ratio of the respective total amounts of neuralgia for the same periods. The average distance of the storm-center at the beginning of the neuralgia attacks was 680 miles. Storms coming from the Pacific coast are felt farthest off, while storms along the Atlantic coast are associated with milder forms of neuralgia, and are not felt until the storm-center is nearer. Rain is not essential in the production of neuralgia. It was found that the severest neuralgic attacks of the year were those accompanying the first snows of November and December. Every storm, as it sweeps across the continent, consists of a vast rain area, at the center of which is a moving space of greatest barometric depression, known as the storm-center, along which the storm moves like a bead on a thread. The rain usually precedes this by 550 to 600 miles; but before and around the rain lies a belt which may be called the neuralgic margin of the storm, and which precedes the rain about 150 miles. This fact is very deceptive, because the sufferer may be on the far edge of the storm-basin of barometric depression, and see nothing of the rain, yet have pain due to the storm.

Physiological Action of Aconite.—From certain experimental inquiries into the physiological action of aconite and its alkaloid, aconitia. Dr. G. H. Mackenzie concludes that these drugs act primarily on the respiration by their influence on the respiratory center and peripheral sensory branches of the vagus nerve. They have no direct action on the heart, and only affect that organ secondarily through the medium of the lungs. Their action on the nervous system consists in firstly irritating and secondly paralyzing the peripheral sensory nerves and posterior roots of the spinal nerves. They have no direct action on the brain or the vaso-motor nerves. They increase the irritability of the peripheral motor nerves, and of the motor columns of the cord. They do not induce muscular paralysis, but, on the contrary, increase the irritability of voluntary muscle. They induce convulsions mainly through their augmenting the irritability of the anterior column of the cord, the motor nerves, and muscles. They firstly increase and secondly diminish temperature. Death ensues from asphyxia and respiratory collapse.