208 INFLUENCE OF TEMPER ATU RE ON THE MAMMALIAN HEART. 



heart whicli was put into tlie warmest vessel beat nnicli more 

 rapidly, and that in the coldest vessel more slowly, than the 

 one which was exposed to a moderate temperature. He also 

 found, although Nysten had failed to observe it, that, just as 

 with the frog's heart, the rabbit's heart which had been put in 

 the warm vessel, and thus caused to beat more quickly, stopped 

 pulsating and lost its irritability by tactile or electrical stimuli 

 much sooner than that in the temperate one. The heart which 

 was put in the cold vessel lost its irritability even sooner than 

 that which was warmed, or rather it seemed to lose it, for the 

 irritability was not destroyed but was merely dormant, and 

 when moderately warmed the heart again became irritable, and 

 remained so for a considerable time. 



I have made several experiments on the effect of temperature 

 on the rabbit's heart while it still remained in the body, some- 

 times leaving all its nervous connections untouched, and some- 

 times dividing the vagi. These experiments were made by 

 lUircotising the animal with opium or chloral, and laying it in 

 a tin vessel about 20 inches long by 6 inches broad, and 3 

 inches deep in the inside, and well padded with cotton wool. 

 The vessel was double, and by pouring hot water into it, the 

 temperature of the rabbit was gradually raised. The belly of 

 the animal was also covered with cotton wool, and sometimes 

 with an india-rubber bag containing hot water. To make 

 respiration easier, a cannula was introduced into the trachea, 

 and in some experiments the inspired air was passed over warm 

 water, so as to warm it and satarate it with moisture and lessen 

 the loss of heat from the lungs. Tlie pulsations of the heart 

 were counted by pushing a line needle through the thoracic walls 

 into the heart, so that it vibrated with each pulsation, and con- 

 necting its outer end, by means of a fine thread, with the lever 

 of one of Marey's cardiographs, which registered the beats on a 

 revolving cylinder covered with smoked paper. ( Vide p. 294.) 

 By means of this arrangement, which I owe to Professor 

 Strieker of Vienna, it is possible to count the pulsations with 

 great exactitude, even when the heart is beating at tlie rate of 

 470 in a minute, as it did in one instance. The temperature 

 was measured by a thermometer in the rectum. As the animals 



