66 SCIENCE PROGRESS 



when it is asked of them. As a measure of the rate at which 

 oxygen is consumed in the different animals we may take either 

 the oxygen-intake or the carbon-dioxide-output of a unit of 

 weight in unit time, as the two things run roughly parallel. In 

 the two following tables the carbon-dioxide-output is given 

 because it happens to be known for a larger number of species 

 than the oxygen-intake. The numbers are for the most part 

 taken from the table in Pembrey's article on " Chemistry of 

 Respiration" in Schafer's Text-book of Physiology and represent 

 the average in round numbers when several results are there 

 given by different observers. Those for birds which are not 

 to be found there are determinations kindly made for me by 

 Dr. C. G. Douglas, Fellow of St. John's College, Oxford.^ The 

 pulse-rates of all the birds and of the smaller mammals have 

 been determined by myself in a manner to be described im- 

 mediately ; those of the larger mammals have been taken on 

 text-book authority when none other was available. As a 

 measure of the volume of blood expelled per beat the weight of 

 the heart in percentage of the body-weight has been taken. 

 This has been determined for a very large number of birds 

 by Parrot (3) but unfortunately not for many of which the 

 pulse-rates are known. For most of these as well as for the 

 mouse I have determined it myself. For most of the other 

 mammals mentioned it has been determined by Bergmann (8) 

 but the results of his observations are referred to, together with 

 some more determinations of his own and of a few other 

 people for other mammals, by Joseph (9). Unfortunately the 

 number of individuals from which the " average," either of 

 pulse-rate or of relative heart-weight, is taken was usually 

 small and sometimes (in all the cases marked with an asterisk) 

 the data were only ascertained from a single individual of a 

 species ; as we know that in other species there is a good deal 

 of individual variation, the numbers given in these columns 

 may not hereafter be found to be the correct averages. They 

 probably are so however in the case of man and the rabbit, in 

 which they have already been ascertained from large numbers 



' For each bird he determined also the oxygen-intake; since this datum for 

 the canary and for the tame duck has not yet been put on record, this occasion 

 maybe used for stating that it was found to be io'99 and r66 grms. per kilo, 

 per hour respectively for the two birds. The canary was remarkably quiet all 

 the time it was under observation. 



