Info. on canine electrocardiograms...

Question
I need this information for an essay I'm working on.
Why are electrodes placed on the legs during an electrocardiogram?

Answer
The placement of ECG electrodes is done in order to detect the electrical conduction which causes the heart to beat as it progresses from the top of the heart to the bottom of the heart. The beginning of the ECG is detected in the arms and on the top of the chest and then the end of the conduction is detected in the legs.

Dr. G.