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XXI. The Dii ■ect Influence of Gradual Variations of Temperature upon the Rate 
of Beat of the Dog's Heart. 
By H. Newell Martin, M.A., M.D., D.Sc.; Professor in the Johns Hopkins 
University, Baltimore, U.S.A. 
Communicated by Dr. M. Foster, Sec. R.S. 
Received December 27, 1882,—Read January 11, 1888. 
[Plates 48, 49.] 
Introduction. 
In the year 1881. I briefly described (1) a method of experimenting- by which the 
heart and lungs of a Dog or Cat could be completely isolated physiologically from the 
remainder of the body of the animal, and kept alive some hours for study in an 
apparently normal condition, the heart beating regularly and maintaining a good 
arterial pressure. Since then I have been at work investigating the influence of 
various conditions upon the pulse-rate of Dogs’ hearts so isolated ; while under my 
supervision several of my pupils have been engaged in studying the work done in a 
unit of time by such hearts under different external conditions. 
As regards the effects of variations of arterial pressure upon the pulse-rate of the 
isolated Dog’s heart, my results have already been published (2) ; and detailed 
observations as to the influence of variations in venous pressure will shortly be 
printed. But in so far as the influence of temperature variations upon the cardiac 
rhythm is concerned, only a brief preliminary announcement (3) has been made. In 
the present paper I propose to give a full account of my experiments upon this 
subject, which is one that, apart from and in addition to its purely physiological 
interest, has considerable practical importance in connexion with inquiries as to the 
immediate cause of the quick pulse so constantly found in warm-blooded animals 
suffering from fever. 
Almost all that we have hitherto known concerning the direct influence of 
temperature changes upon the cardiac rhythm is derived from experiments made 
upon cold-blooded animals, especially Frogs. As regards these animals all observers 
are agreed that as the temperature of the heart is gradually raised from near zero to 
about 40 C., its beat is quickened. It is clear, however, that we can only argue with 
4 Q 2 
