Collected papers (Part I.) from the Research Laboratories of the Royal College of Physicians, London, and the Royal College of Surgeons, England / edited by T.G. Brodie.

Date:
1903
Catalogue details

Licence: In copyright

Credit: Collected papers (Part I.) from the Research Laboratories of the Royal College of Physicians, London, and the Royal College of Surgeons, England / edited by T.G. Brodie. Source: Wellcome Collection.

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    membrane which are to form joints in the bellows should be un- touched by the varnish so that they may remain quite flexible. This is especially important at the hinge. When the spirit varnish has thoroughly dried the bellows are folded. The folding should be carried out so that the face opposite the hinge folds inwards to lie between cover and base, whereas the sides are folded outwards (see Fig. 1). The whole is now coated with a varnish made by diluting boiled linseed oil with three times its volume of xylol. Two or three coats of this are applied at intervals of about half-an-hour. This makes the whole air-tight, but the flexibility still remains. Should the bellows at any time become too stiff all that is necessary is to paint them with xylol, and if they leak a coat of the drying oil varnish will, if they are properly made, at once render them air-tight again. They may be used while still wet if care be taken that the wet surfaces do not touoh one another. In making large bellows-recorders I find it of advantage to make those parts which do not bend of paper, rather than of peritoneal mem- brane, because the latter is rather too pliable in large surfaces. All the bending parts must be made of the more flexible peritoneal membrane. I have given so many of the details of the manufacture of the recorders because it is quite easy to make them for oneself. They are also now being made by the Cambridge Scientific Instrument Company. Air blown into the bellows lifts the cover which rotates about the hinge, and to record these movements is very simple. No further joint is required—all that is necessary is to attach a writing lever of the necessary length to the cover of the bellows at right angles to the hinge. If it is wished, the cover and writing lever may be counter- poised by a small weight, but this only adds to the inertia, and I therefore usually work without one. The advantages of this form of recorder are the following :— (а) It is always ready for immediate use and requires no preliminary adjustment. (б) It wears well and is not easily damaged. (c) It is extremely sensitive. (d) It can be made of any capacity, and even with very large ones the weight of the moving parts is minimal. The last point is, perhaps, its greatest advantage. I have at present in use four different sizes. The smallest is 30 mm. long and 20 mm.