Page:Popular Science Monthly Volume 12.djvu/264

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THE POPULAR SCIENCE MONTHLY.
 

Local Temperatures of the Blood.—From researches made by Claude Bernard, it appears that while the temperature of the blood in the aorta and its more important branches is uniform, that of the venous blood varies considerably in different regions of the inferior vena cava and its principal tributaries. At the junction of the extremities and the neck with the trunk of the body, the venous blood is colder than that in the great arteries; in the right heart it is considerably hotter. If we determine its temperature at successive points in the inferior cava, we find that at the junction of the iliac veins this is lower than the arterial temperature: on a level with the entrance of the renal veins, the two are about equal; on a level with the hepatic veins, the temperature of the venous exceeds that of the arterial blood by nine-tenths of a degree. It retains this superiority even after it has become mixed in the right heart with the colder blood returned through the superior cava. Accordingly, though the venous blood of the peripheral parts is colder than in the arteries, it acquires sufficient heat during its passage through the abdominal cavity, not merely to equalize the difference, but actually to give it a permanent advantage. This is so, not because the viscera are the source of animal heat, but simply because they are by their situation protected from the effects of radiation and evaporation. Heat is generated in all the tissues, muscles, nerves, nerve-centres, and glands. The rise of temperature, which may always be detected in a muscle when thrown into a state of contraction, is invariably preceded by a slight depression; and precisely the same phenomenon is exhibited by a gland when its secretory nerve is stimulated.

 

Electro-Plating.—We take from Van Nostrand's Engineering Magazine the following statement of the results obtained by Bertram! in experiments in electro-plating with aluminium, magnesium, cadmium, bismuth, antimony, and palladium. Aluminium was deposited on decomposing, with a strong battery a solution of the double chloride of aluminium and ammonium; a plate of copper forming the negative pole whitens gradually, and becomes covered with a layer of aluminium, which takes a good polish. The double chloride of magnesium and ammonium in an aqueous solution is readily decomposed by the battery, giving in a few minutes strongly-adherent and homogeneous deposits of magnesium on a sheet of copper. It polishes readily. The battery must be powerful. Cadmium is best deposited from the bromide to which a little sulphuric acid has been added; it is then very coherent and very white, and takes a fine polish. The sulphate, if acidulated, also gives an immediate deposit of metallic cadmium, very adhesive and capable of a good polish. Bismuth is deposited from a solution of the double chloride of bismuth and ammonium on copper or brass. by the current from a Bunsen element; it is very adhesive, and might be used in decorating works of art. Antimony can be deposited from a solution of the double chloride of antimony and ammonium at common temperatures. Deposits of palladium are obtained with ease by means of the double chloride of palladium and ammonium, either with or without the battery. The solution must be perfectly neutral.

 

New Method of Artificial Respiration.—Dr. Benjamin Howard, late of the Long Island Medical College, recently gave at King's College Hospital, London, a demonstration of his "direct method" of producing artificial respiration. For the purpose of making his description of the method perfectly plain, Dr. Howard had a man to act the part of a person rescued from the water, and apparently dead from drowning. The first thing done was to rip away the wet clothing to the waist, making of it a large, firm bolster. "Quickly turning the face downward," said he, as he proceeded to explain the process, "the bolster beneath the epigastrium, making that the highest point, the mouth the lowest; placing both hands on his back immediately above the bolster, my whole weight is thrown forcibly forward, compressing the stomach and lower part of the chest between my hands and the bolster for a few seconds, two or three times, with very short intervals." Thus the lungs are relieved of water and the stomach emptied. Then "quickly turn the patient on his back, the bolster again making the epigastrium