Abstract
In November, 1921, the writer made routine electrocardiograms of Dr. Sutherland Simpson's group of experimental cretin lambs and the control normal lambs.
The three leads employed were the same as those used in the usual human electrocardiograms. Soft sheet lead electrodes were bound on the clipped upper leg of the sheep by means of cloth strips wet with saturated salt solution. The lambs stood in the normal position.
A brief review of Dr. Simpson's treatment of the sheep is essential in interpreting the results.
In Group I there were 4 pairs of twin lambs. One of each pair had been operated upon when from 6 to 8 weeks old and both lobes of the thyroid removed. The other was left unoperated as a control.
Two of the operated lambs began to receive thyroxin sub-cutaneously, beginning 17 to 21 weeks after the operation and lasting until the electrocardiograms were taken. The period of treatment was approximately one month.
The electrocardiograms of the cretins which had received no treatment definitely differed from the normal. In these former the P and Q waves were either absent or just discernable in all derivations. The R and T waves were very small; the latter being negative in all cases. This is the normal direction for this final deflection in the sheep electrocardiogram.
In the case of the cretins which had received thyroxin the P waves were nearly normal in height in all derivations; there were definite Q waves; the R waves were increased in height and the T waves were larger and positive in direction.
In Group I1 there were 5 pairs of twin lambs. Of 4 pairs of these twins, one of each pair was completely thyroidectomized when 4 to 6 weeks old. 30 weeks later each of these operated lambs received treatment for 15 weeks and electrocardiograms were taken 28 weeks after treatment was stopped.
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