212 INFLUENCE OF TEMPERATURE ON THE MAMMALIAN HEART. 



ened the power of the vagus diminished; but when the tem- 

 perature had risen nearly to the upper limit, and the pulsations 

 were becoming slow, the power of the vagus again increased, 

 and, contrary to my expectation, was strongly marked just 

 before the heart ceased to beat. Few as these experiments are, 

 the results are so definite that we may, I think, conclude that 

 in the heart of the rabbit, and probably other mammalian 

 hearts, a temperature sufficiently high to produce stoppage of 

 the heart does not paralyse the vagus or the inhibitory appa- 

 ratus through which it acts. It is possible that a longer 

 exposure to a high temperature, such as occurs in fevers, may 

 produce this result; but it seems probable that it is not so, 

 and that if digitalis, or other similar drugs, should not act on 

 the pulse during fever, we must seek for some other explanation 

 of their failure than paralysis of the structures through which 

 they act. Unfortunately I did not carefully look for clots in 

 the vessels after death ; but on dividing the carotids and jugulars 

 the animals bled freely, and in one which I examined no trace 

 of a clot could be found in the heart or vena cava. I am inclined, 

 therefore, to reject Weikart's* hypothesis that death from heat 

 is due to coagulation of blood in the vessels, and rather to look 

 on the impairment of the muscular power of the heart by the 

 heat, possibly from coagulation of the myosin in its muscular 

 substance, as the cause of death, as suggested by Bernard,! and 

 to regard the rapid loss of irritability, noticed by Panum, in the 

 heart exposed to a high temperature, and therefore beating 

 quickly, as an indication of the great importance of keeping 

 down the temperature and pulse-rate in fever patients by every 

 means in our power. 



I gle.dly take this opportunity of expressing my thanks to 

 Professor Burden Sanderson for the kindness with which he 

 placed his apparatus at my disposal and allowed me the use of 

 his laboratory in which the greater number of my experiments- 

 were performed. 



Experiment I. — A young rabbit was fastened in the apparatus- 

 and narcotised by the injection of 1^ cub. cent, of laudanum 



* Arch. d. Heilk., p. 193, 18^:3. 



t BcruarJ, Compte-rend. de La Soc. de Biolojie, p. 51, 1S59. 



