548 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



still higher than before when the heart stopped from heat, the condition 

 of heat-tetanus will pass into that of " heat-rigor," and no application 

 of cold will have the slightest effect toward again starting the heart. 



The influence of heat and cold on the amount of work done by the 

 heart is an extremely complicated subject. We can only state here that 

 within certain limits the mechanical work done by the heart increases 

 with an increase of temperature, but that very soon the contractions 

 increase in number in much greater proportion than the mechanical 

 effect ; hence, though the amount of work done at a comparatively high 

 temperature is greater than can be accomplished at a low temperature, 

 the effect of each individual contraction is much less. 



The frequency of the normal rate of contraction of the heart varies 

 greatly in different animals, as shown in the following table compiled by 

 Colin:— 



Frequency of the Pulse per Minute. „ , - 



In the elephant 25 to 28 



camel 28 to 32 



giraffe 66 



horse 36 to 40 c -- * ^ to 



ox 45 to 50 /-^i- -?, 



mule, . 46 to 50 



" tapir 44 



ass, . . . . . . . . 46 to 50 



pig, • . . . . . . . 70 to 80 



" lion, 40 



" lioness, 68 



tiger, 64 



sheep, 70 to 80 



goat, 70 to 80 



" leopard 60 



" female wolf, 96 



" hyena 55 



dog 90 to 100 . - 



cat 120 to 140 



rabbit 120 to 150 



" marmot 90 to 175 



" mouse, . 120 



goose 110 



" chicken, 140 



pigeon 136 to 138 



" snake, 24 



carp 20 



frog 80 



" salamander, 77 



The following table shows the variation and frequency of the pulse 

 per minute in the horse and ox at different ages : — 

 Horse. Ox. 



Newborn, .... 100-120 Newborn 92-132 



Fourteen days old, . 80- 96 Fourteen days old, . 68 



One-fourth year old, 68- 76 One-fourth year old, . . 



One-half year old, . 64- 72 One-half year old, . 50- 68 



. One year old, ... 48- 56 One year old, . . 50-68 



Two to three years, . 40- 48 Young cow, ... 64 



Four years of age, . 38-50 Four-year-old ox, . 56 



Aged, 32-40 Aged, 45-50 



