Page:Popular Science Monthly Volume 14.djvu/262

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linger adds, and his warning will carry great weight, "is an important matter, and, although likely to be in practice neglected at first by the public, may probably impress itself upon them in an unwelcome manner"—that is, by a serious outbreak of trichinosis, or some other form of parasitic disease.


Cultivating Disease.—The virulence of the yellow fever in Memphis is easy to account for when the sanitary conditions of that city are understood. Two or three years ago we published some mortality statistics concerning this place, which appeared to show that it is exceptionally unhealthy. It would indeed be nothing short of a miracle if Memphis were a healthy city with its highly insanitary surroundings. The situation is thus described in the Lancet mid Clinic, by Dr. S. H. Collins, a Cincinnati physician, who rendered efficient service in Memphis as a volunteer during the prevalence of the epidemic: "Memphis is situated upon the east bank of the Mississippi, upon a bluff varying from fifteen to fifty feet in height. Upon the crest of this bluff runs Front Street; from this street the ground slopes eastwardly away from the river, so that all rain, surface-gutter washings, slop, and whatever of floatable filth there may be, is drained into the bayou, which winds about through the heart of the city. Across the river the Arkansas shore stretches low and flat, a vast marsh, notorious for its malaria; north and east of Memphis upon the Tennessee side, the land is low and swampy; the soil in and about the city, of clay. The bayou runs through the most thickly-populated parts of Memphis; into this elongated cesspool is collected all the floating filth of a city of 55,000 inhabitants; garbage, the drainings from privy-vaults, gutter and street washings, dead animal matter, all and everything is poured or thrown into this receptacle, there to decay and fester under the broiling sun of that southern climate. Consider it, if possible—ten miles of reeking rottenness! Not a yard of it covered except where crossed by the bridges of the various streets. During a rise of the Mississippi the back-water fills this bayou bank-full, its accumulated filth then soaking into the clay of its banks. When the river falls, the current of the bayou is not of sufficient strength to empty its contents into the river. The streets of the city of Memphis are beyond description filthy, and completely out of repair; the wooden pavement is the one in use, or rather was the pavement originally put down. The streets and yards are heavily shaded—the magnolia being the tree mostly used."


The Movements of Plants.—After much patient study of the phenomena known as heliotropism and the sleeping and awaking of plants, M. Paul Bert, in a memoir addressed to the Paris Academy of Sciences, an abstract of which is published in the Revue Scientifique, offers an ingenious theory to account for them. The swelling of the flower or leaf stem just below these organs has long been recognized as the seat of the movements in question, and hence it has been called the "motor-swelling" (renflement moteur). The movements are directly produced by changes in the energy with which the renflement moteur supports the flower or leaf, and this energy is greatest at night. For a long time the author was baffled in his investigation of the matter constituting the "motor-swelling." Nevertheless, after a protracted series of minute observations, he recognized in the glucose the fundamental cause of the periodic movements. It is known that this substance is formed under the action of solar light, that it is decomposed in darkness, or that it migrates and sometimes accumulates at different points of the plant organism. Now, one of these points is the renflement moteur, and it is very plain that its quantity there varies at the different stages of the diurnal life of the plant. Thus the greater part of the phenomenon is due to the storing up and then to the destruction of the glucose, the hydration of which produces the energy of the motor-spring. The same explanation serves to account for heliotropism, another phenomenon due to the action of the highly refracting rays of the spectrum on glucose or on its hydration. Inasmuch as the action of these rays lessens the tension on that side of the "motor-swelling" on which they fall, the opposite side gains a relative increase of energy, and hence results a certain motion; and, as the sun moves on