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NOXIOUS INSECTS. 



NUTRITIVE VALUES OF FOOD. 



poplar and the aspen are subject to similar dis- 

 eases, which are found to be accompanied by 

 tha multiplication of bacteria. 



The cause of the mysterious failure of sugar- 

 beets, on land on which this crop has been 

 raised for many years in succession, has been 

 found to be a minute parasite, which is 

 nourished by the decaying roots. The experi- 

 ments of Kuhn and others, which led to the 

 discovery of the parasite, show that the soil 

 first becomes infertile in patches, where the 

 plants begin to die, from which centers the 

 beat-sickness, as the phenomenon is called, ex- 

 tends over the entire field, and is capable of 

 spreading through whole districts. It was sup- 

 posed until the recent discovery, as it is in the 

 cases of other crops which languish or fail after 

 repeated plantings on the same soil, that it was 

 due to the exhaustion of certain soluble ma- 

 terials in the soil which are specially required 

 for tho particular plant. Analyses of soils 

 showed no deficiency of nutrient elements in 

 the case of the beet-sickness. Chiccory, which 

 requires the same kind of soil as the beet, flour- 

 ished in the sickened soil. Other vegetables of 

 many kinds planted in an infected field were at- 

 tacked. The roots of the young beets, it was 

 found, were attacked by the parasites, and 

 their larva lodga in them. Of different reme- 

 dies tried, the most practicable is to sow tho 

 field thickly with beets, and then pull up the 

 entire young crop, and, by burning it, destroy 

 the insacts after they have pierced the roots. 



Experiments with prussic or hydrocyanic 

 acid, conducted by Dr. Franz Konig, prove 

 that it is the best disinfectant for plants in- 

 fested with animal parasites. An atmosphere 

 in which only one third gramme of the acid is 

 diffused in every cubic metre of the air, a quan- 

 tity which is not fatal to the tenderest parts of 

 plants, will destroy the phylloxera and its eggs 

 in half an hour's exposure. Prussic acid is less 

 injurious to some plants than to others, but its 

 action on animals is much more violent than 

 on any plants. Large winged insacts die in an 

 atmosphere containing only one tenth gramme 

 to the cubic metre. Robust, woody plants, with . 

 their leaves and flowers, can stand a gramma of 

 the acid to the cubic metre of air. 



The remedies for phylloxera, brought for- 

 ward at a congress called at Bordeaux for the 

 discussion of the subject, were submersion of 

 the vineyards, and the application of bisulphide 

 of carbon and sulpho-carbonates. The plans of 

 grafting French varieties of grape upon Ameri- 

 can stems, or American vines on French stems, 

 are found to produce plants which are usually 

 proof against the insect-pest. 



Two kinds of insecticides are known which 

 are completely effective, and at the same time 

 harmless to vegetation. These are fatty sub- 

 stances, and a certain group of composite flow- 

 ers. An oily substance, when it can be applied 

 so as to cover the surface of the insect's body 

 in a film, causes instantaneous death by suffoca- 

 tion. - It closes the spiracles, and excludes the 



air from the tracheal tubes. There are, 

 ever, but few cases in which this insecticide 

 can be administered. The other remedy against 

 destructive insects finds a very extensive appli- 

 cation in the form of a powder called com- 

 monly " Persian insect-powder." It is made 

 from flowers of the Anthemis group. It de- 

 stroys insects, by paralyzing their nervous sys- 

 tem. The mode of its action is not understood. 

 To all other life it seems to be almost innocuous. 

 The most efficacious of these flowers are species 

 of the genus Pyrethrum. The common Artemi- 

 sia fill/olio, is sufficiently powerful to destroy 

 delicate insect forms. Instances have occurred 

 recently in which the Persian powder has acted 

 injuriously on vertebrate animals. 



NUTRITIVE INGREDIENTS AND VAL- 

 UES OF THE FOOD WE EAT. Among the 

 numerous branches of biological research, one, 

 and by no means the least interesting and im- 

 portant, is the study of foods and nutrition. 

 "Within the past fifteen years especially, a very 

 large amount of scientific labor has been de- 

 voted to the investigation of the composition 

 of foods and the function of their ingredients 

 in the animal economy. Indeed, very few per 

 sons this side of the Atlantic have any just con- 

 ception of the magnitude of this work and 

 its results. And, though many of the most 

 important problems are still unsolved and 

 must, because of their complexity, long re- 

 main so, yet enough has been done to give us 

 a tolerably clear insight into the processes by 

 which the food we eat supplies our bodily 

 wants. 



The bulk of our best definite knowledge of 

 these matters comes from direct experiments 

 in which animals are supplied with food of 

 various kinds, and the effects noted. The food, 

 the excrement, solid and liquid, and in some 

 cases the inhaled and exhaled air, are meas- 

 ured, weighed, and analyzed. Many trials 

 have been made with different animals, horses, 

 oxen, cows, sheep, goats, swine, dogs, rabbits, 

 birds, and the like, and a considerable number 

 with human beings of both sexes and different 

 ages. In the philosophical planning of the 

 researches, in the ingenuity manifested in de- 

 vising apparatus, in the accuracy, thorough- 

 ness, patience in execution, and magnitude of 

 the work, as well as in the distinguished genius 

 of many of the workers, chemico-physiological 

 science has here, as in other specialties, assumed 

 the highest rank among the sciences of our time. 

 "With the rest it has brought us where we can 

 estimate the nutritive values of foods from their 

 chemical composition with so near an approach 

 to accuracy that in Germany, where the best 

 research is done, tables, giving in figures the 

 composition and nutritive valuations of foods, 

 have been prepared by eminent physiologists, 

 and are coming into general use among the 

 people. To give a brief account of the out- 

 come of such work as this in its relation to the 

 nutritive values of foods is the chief object of 

 this article. 



