494 



ANNUAL, KEPORT SMITHSONIAN INSTITUTION, 1910. 



one of — ' ^ ' — -=319, considering also the small size of its heart. 



If we were to take the carbon-dioxide output of the thrush as being, 

 as from the size of the bird it is likely to be, about 10 grams per 

 kilo per hour we should have expected its pulse rate, by comparison 

 with that of the sparrow to have been about 666 per minute were it 

 not for the large size of its heart, which makes us expect instead one 

 of only 225 j^er minute. From what is known of the metabolism of 

 the goose, we should expect its pulse rate to be about 144 per minute 

 when it is in good condition ; we should expect that of the wild duck 

 to be not much more than half that of the tame, allowing for its car- 

 bon-dioxide output per kilo per hour being, on account of its smaller 

 size, somewhat less than what Mr. Douglas found it to be in the 

 tame duck of which the pulse rate was recorded. Small hearts and 

 correspondingly quick pulses seem, therefore, to be more character- 

 istic of tame birds than of wild, a subject to which we shall have to 



return. 



Table II. — Mammnls. 



Weight in grams. 



25 

 300—500 



2,000—6,000 



6, 000—10, 000 

 10, 000— .50, 000 



20,000—100,000 

 400, 000—600, 000 



Mamma J. 



Mouse 



Guinea pig . 

 Small dog . . 



Cat 



Rabbit 



Hare 



Medium dog 

 Large dog . . 



[Deer 



[Sheep 



Pig 



[Man 



fOx 



■^ Horse 



I Race horse . 



Average 

 carbon- 

 dioxide 

 per kilo 

 per hour 

 (in grams). 



8.4 

 1.8 

 1.5 

 1.3 

 1.2 



(?) 



1.37 

 1. 



(?) 



(?) 



.6 



.45 



.3 



(?) 



Average 



heart 



weight in 



percentage 



of body 



weight. 



.79(4) (2) 



.40(9) 



.9(9) 



.45(9) 



.27(9) 



.75(B) 



.75(9) 



(?) 

 .15(8) 

 .60(8) 

 .45(8) 

 .59(8) 

 .39(8) 

 .63(8) 



.12(13) 



Frequency of beat per 

 minute. 



Observed 



average 



when at 



rest. 



700(<) 

 300(7) 

 (?) 

 160(7) (1=) 

 205(11) 



64(12) 

 120(7) 



85(7) 



(?) 

 75 

 75 

 70= 

 48 

 37 



(?) 



Average to 

 be expect- 

 ed by com- 

 parison 

 with man. 



732 

 309 

 115 



198 

 306 



(?) 



(?) 



A5? 

 80 

 100? 

 70 

 78 

 34 



(?) 



In the table for mammals a column has been added giving the 

 pulse rate, which, taking both carbon-dioxide output and relative 

 heart weight into consideration, we should expect the animal to 

 have compared with man. Man has been chosen as the standard 

 because so many more observations have been made on him that the 

 averages are more likely to be correct than those for the others, with 

 the exception perhaps of the rabbit. Of course, somewhat different 



