On the influences which modify the work of the heart / by Charles S. Roy.

Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: On the influences which modify the work of the heart / by Charles S. Roy. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    obtained in Great Britain. When moistened with water or glycerine its flexibility leaves nothing to be desired, and its comparative inexten- sibility specially fits it for the instrument in question. I have found it of great service in the construction of other apparatus for physiological work. A piece of this membrane is so fastened on the end of the little cylinder of the instrument, that it can move freely up or down. This will be more intelligible on referring to Fig. 3. Through the middle of the membrane (k) passes a needle (e) which is fixed in the centre of the light aluminium piston (l). The lower surface of this piston, which lies on the inner side of the membrane, is fixed to the latter by a little varnish (this is done before the membrane is tied on, while it is still dry), although this is not absolutely necessary, since the valve-like action of the membrane, when the instrument is in use, renders the hole made by the needle air-tight. The diameter of the piston is less by T5 mm. than that of the interior of the cylinder in which it is placed, so that it can move freely up and down without friction. It is kept in the centre of the cylinder by means of the guide (d) through which the needle passes. The friction is thus reduced to a minimum. The lower end of the needle is connected, by a fine hook (/), to the sliding part of a light lever, whose duty it is to magnify, to any de- sired extent, the movements of the piston. The lever is made of a slip of straw supplied with a delicate aluminium point. The mem- brane, it should be added, although it be so thin and flexible, is more than strong enough for the purpose required, and, after being once fastened on and moistened with glycerine, will serve for hundreds of observations without requiring renewal. The ventricle, or auricles, as the case may be, having been fastened on, and the cannula and the reservoirs filled with the diluted blood which is destined to feed the portion of the heart, this latter is intro- duced into the bell-glass (which has been previously fixed on the plate, and its cavity filled with olive oil), which is closed above by the stopper through which the cannula passes*. On now opening the stop- cock e (Fig. 1), the oil begins to flow out through the tube f diminishing * As the membrane which closes the lower opening of the vessel which contains the heart is permeable to aqueous fluids, it is necessary to use oil with this instrument. This is no disadvantage, seeing that pure olive oil is decidedly preferable to salt solution, which is usually employed to protect the heart, in experiments of this kind, from the action of the air. I have never met with the slightest reason for supposing that oil either stimulates or affects the vitality of the tissue of the heart with which it comes in contact.