426 



Scientific Proceedings (124). 



grams 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 es- 

 sential 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 II 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 

 Iambs received treatment for 15 weeks and electrocardiograms 

 were taken 28 weeks after treatment was stopped. 



The cretin treated with Nal in the feed, and the one treated 

 with thyroxin subcutaneously, showed the typical cretin electro- 

 cardiograms. Of the two lambs given thyroid extract in the feed, 

 one showed an electrocardiogram slightly more normal than that 

 of the untreated cretin, and the other presented an almost normal 

 electrocardiogram. 



