Coronary blood flow, oxygen consumption of the myocardium and cardiac work were determined in the sheep by means of a by-pass preparation of the right heart, previously employed in the dog.
The results showed that, as in the dog, coronary blood flow in the sheep is closely correlated with myocardial 02 consumption, whereas it is correlated to a lesser degree with arterial pressure and cardiac output; the sheep, however, differs from the dog mainly in the very low work capacity of its myoeardium.
Because of this low capacity of haemodynamie work observed in the sheep by-pass preparation, the authors do not feel that the sheep can replace the dog to further the aims of circulation research.
Although the sheep has been frequently used in studies on the cardiovascular system (Nos~DA et al., A~GI~ISAm et al., CAM~A et al., LUISADA et al.), there is little information regarding the cardiovascular function of this animal and the differences between it and the dog, an animal which has played a much more frequent role in experimental studies (KATz, RODBARD et al., AImLLA et al., MA~eI~TTI et al., etc.).
We had available in our laboratory a technique specially adapted to the investigation of coronary circulation, which we were using frequently in experiments on dogs.
Consequently we were able to carry out a careful study of the coronary haemodynamics in the sheep which were presumed to differ from those in the dog in the following ways, bearing in mind the constitution, the feeding, and the living habits of this animal, i.e.
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Low muscular activity;
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the presence of the rnmen that, owing to its size, could act mechanically or by reflexes of the internal organs on the cardiac function;