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FURTHER REMARKS ON THE TECHNIQUEOF ELECTROCARDIOGRAPHY.

To the Editor of THE LANCET.

SIR,-During the last week I have had the opportunity ofexamining and taking records by a new instrument con-structed by Messrs. Siemens. The essential part of the

apparatus-viz., the galvanometer-consists of a fine sus-

the Einthoven (Cambridge model) and of the Bock-Thoma.The accessories for illuminating and recording purposes arevery compactly and conveniently arranged.

I take this opportunity of rectifying a mistake in the

setting up of the figures illustrating my article in the issue ofTHE LANCET of August 9th. Figs. 2A and 3A on page 381have been reproduced mirror fashion, so that their com-

parison with the corresponding Figs. 2A and 2B is impossibleto any but an expert. The actual comparison is as

follows :-

FIG.2A.

Cambridge string galvanometer.

FM.2B.

Bock-Thoma oscillograph.

FIG. 3A.

Cambridge string galvanometer.

FIG. 3B.

Bock-Thoma oscilloraph.

pended coil in a moderately powerful magnetic field, andthe movements are magnified by optical lever at a distanceof 1 metre. The suspended system is hermetically enclosed,so that there is no variation of tension of any stretchedfibre. The damping of the deflections is electromagneticand is very easily controlled, so that the indication can bemade perfectly dead-beat or with any desired amount ofovershoot. Its sensitiveness considerably exceeds that of

I am, Sir, yours faithfully,A. D. WALLER.

The Physiological Laboratory, University of London, S.W.,August 18th, 1913.

* We saw and regretted the mistake of the illustrator,but too late for rectification, the illustrations being receiveda very short time before we went to press.-ED. L.