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He estimates the occurrence or non-occurrence of ædema by the specific gravity of the blood and blood-plasma, arterial and venous, of mascle and of skin, regarding these as more delicate tests of the presence or absence of oedema than the rougher methods of inspection, measurement, and pitting on pressure.
Having raised the pressure in the femoral vein to 50 mm. of mercury, he finds that there is no alteration in the specific gravity of the blood or blood-plasma of the muscle or of the skin, nor is there any increase in the amount of the lymph-flow, though such a pressure be maintained constant for an hour.
In the affected limb only is any change to be noted, and here there s a rise in the specific gravity of the venous blood and hlood-plasma, which depends upon the longer sojourn of the blood in the limb and the consequent greater removal of the more watery portion from a given volume of blood.
Inasmuch as it is essential upon a purely mechanical explanation that the exudation from the blood-vessels should be increased in amonnt synchronously with the increase of pressure, and no such exudation is found to take place during an hour after the pressure in the veins has been raised, the author considers that the mechanical explanation is not supported by facts.
Since all forms of oedema are accompanied by an insufficient supply of blood to meet the requirements of the tissues, the author investi. gated the effect of different varieties of anæmia
the occurrence of oedema. The varieties investigated were :
1. Prolonged complete anæmia, lasting three hours. 2. Hæmostasis, or cutting-off of the limb, with whatever blood
and lymph it may contain, from the rest of the circulation,
by means of a tight ligature, for one hour. 3. Complete anæmia combined with stimulation of the sciatic
nerve, and persistence, in situ, of the products of muscle
metabolism, the whole lasting one hour. After each of these three varieties of anæmia the effects of active congestion, and of venous obstruction, were separately considered.
It was found that ædema occurs, as shown by a fall in the specific gravity of the muscle and skin, and a rise in the specific gravity of the blood, after all these conditions of anæmia, and the author concludes, therefore, that starvation of the tissues plays an important part in the occurrence of ædema. ... The amount of medema obtained, however, was found to be greater in those cases in which the limb had been subjected to the action of venous blood, and the longer the action of the venous blood was allowed to obtain, the greater the amount of edema. The author concludes that the presence of the products of tissue metabolism at the site of their formation plays a part in the occurrence of oedema even more important than that played by starvation.
The greatest amount of ædema was obtained with venous obstruction after anæmia and stimulation of the sciatic nerve.
The author shows that stimulation of the nerve of a muscle normally produces changes which lead to an absorption of water by the muscle, and he concludes that the ædema which accompanies passive congestion depends upon an excess of the normal process whereby the nutrition of the tissues and the removal of the waste products of their metabolism are carried out, the supply of lymph being excessive only because the demands of the tissues are excessive.
The part played by the blood-vessels the author regards as somewhat uncertain. Sharing in the general starvation of the limb, their function must be modified in some as yet unrecognised way; nevertheless, he considers that the part played by them is subordinate to the part played by the tissues outside the blood-vessels.
Presents, January 25, 1894. Transactions. Berlin :-Gesellschaft für Erdkunde. Zeitschrift. Bd. XXVIII. No. 5. 8vo. Berlin 1893.
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** On Copper Electrolysis in Vacuo.” By WILLIAM GANNON,
M.A., “1851 Exhibition” Scholar, Queen’s College,
Received November 14,-Read December 7, 1893.
The electrolysis of copper salts is interesting, not only theoretically as affording a verification of Faraday's Law of Electrolytes, but also practically on account of its constant use in the graduation of currentmeasuring instruments, such as tangent galvanometers and ammeters. It is known that copper sulphate in solution does not conform rigorously to the simple form in which Faraday's law is generally expressed. Gray,* who made a detailed examination of the electrolysis of copper sulphate, found that the weight of the deposit is very variable in neutral solutions for the same current and the same interval of time; and he also showed that, in solutions containing a little free sulphuric acid, this inconstancy was removed, but that the weight was a function of the temperature of the solution and of the current density at the cathode. His results with acid solutions are graphically represented by curves (partly reproduced at the end of
* 'Phil. Mag.,' vols. 22 and 25 (1886–88).
this paper), an inspection of which shows that the deposit is heavier the higher the current density and the lower the temperature. (“Carrent density” is defined as the ratio of the value of the current in ampères to the total immersed surface of the cathode plate.) A very possible explanation of this anomaly is furnished by the work of Gore* and Gray,who independently found that copper dissolves to a very appreciable, though variable, amount in solutions of copper sulphate.
The secondary chemical reactions which follow-chiefly the formation of basic salts—complicate the electrolysis. This corrosion of copper plates in the sulphate solation is much diminished if a little free sulphuric acid is present, with the result that the electrolysis of acid solutions yields more consistent results than are obtainable with nearly neutral solutions. Now, Schustert found that the loss in weight of copper plates in a solution of copper sulphate does not occur if the air be removed from the solution. It is therefore very probable that it is the oxygen of the air present in the solution that causes this chemical corrosion; and hence it was of interest to examine if any difference could be found between the weights of the deposits of two copper voltameters, one of which would be placed in vacuo. Schuster and Crossley showed that the silver deposit is slightly greater in vacuo than in air; and the experiments tabulated in this paper point out, with certain limitations, a similar result.
The plan of these experiments was simple. The same current passed through two voltameters connected in series, one being under the ordinary atmospheric pressure and the other in a partial vacuum. The voltameters, in most of the experiments, consisted of ordinary glass beakers, containing the solutions of copper sulphate, into which dipped three parallel copper plates of the same size, the centre one acting as the cathode, and the side ones forming a double anode. The plates were held in position by means of German silver clips pressing against vertical brass supports which were attached to an ebonite framework. One voltameter was placed in an inverted bell. jar, into the neck (lower part) of which was fitted an india-rubber cork. Through the cork, which was coated with Faraday cement, passed three glass tubes, one connected with an exhaust pump and the remaining two containing the leads. In some of the experiments another tube was introduced, through which was passed into the jar a stream of nitrogen gas previous to exhaustion ; but as this did not give any better results, it was discarded. At the bottom of the bell-jar inside was a support for the beaker, and on the latter rested * "Nature,' vol. 25, p.
See “Note” at end of this paper.