78S MR. A. SUTHERLAND ON THE [Juiie 20, 



years of observation will be necessary, and much gathering of 

 facts such as, to a certain extent. Dr. Pembery has collected in the 

 paper contributed by him to Sehaefer's ' Physiology.' These will 

 no doubt give an nltimate foundation for a satisfactory theory, 

 which is as yet impossible. 



Among these preliminary facts there must be many observations 

 of the normal temperature of all species of animals, but more 

 particularly of those birds and mammals which form the link 

 between their own classes and the reptile class below them. Out 

 in Australia, and under favourable conditions, I made, during 

 two years, daily observations on the temperatures of monotremes 

 and marsupials, and was able to show, in a paper ■i)ublished last 

 year in ' Nature,' that those Oi'ders which are structurally lowest, and 

 therefore lowest in classification, are also lowest in temperature of 

 all the mammals and form indubitably a chain of coiuiecting-links 

 between the cold-blooded and the warm-blooded condition. It is 

 clear that up to a certain point increasing temperature has been 

 a concomitant, perhaps a factor of general progress. Not, 

 however, that the highest animal will always necessarily be the 

 highest in temperature. Because, after a certain limit has been 

 reached, progress is rather shown in perfecting the apparatus that 

 secures a uniformity of temperature. Por to all animals there is 

 a limit beyond which it is fatal to go. A frog will begin to 

 collapse at 32° C. (90° P.). A man is normal at 37°, but begins to 

 collapse at 41°, and is beyond the hope of recovery if his tem- 

 perature reaches 42° (107°'6 P.), Birds in general are normal about 

 42°, but perish at 45° (113° P.). 



The process of development, therefore, is to carry an animal up 

 to that temperature at Avhich its metabolism will produce the most 

 healthful activity, and, after that, to make the animal secure 

 against dangerous variations from that standard. This process 

 finds its perfection in man, who can sit with little inconvenience 

 for an hour or two in an oven, where the heat would be such as 

 to kill a rabbit in ten minutes. 



Up to a certain point, however, the temperature of animals is 

 closely concomitant with their rank in the zoological classification. 

 The monotremes are the coldest-blooded of all mammals and the 

 least able to maintain a uniform temperature, the lower genus, 

 Omithorhynchiis, being also the les^ gifted in these respects. The 

 other genus. Echidna, leads us a step higher and forms a link 

 towards the lowest marsupials, among which family after iamily 

 carries us steadily up to the characteristic mammalian temperature. 



Having in a general way ascertained that this is the Cfise with 

 mammals, I was very anxious to do the same with birds, but 

 have never had a chance until the Society's Gardens placed it 

 in my way. Although the Apteryx, which structurally is the 

 lowest of birds, is a native of New Zealand, 1 have never seen one 

 in Australia on which to make observations. But on visiting 

 London I received from Mr. Sclater and Mr. Bartlett courteous 

 permission and a generous co-operation in taking the temperatures 



