OCR Text |
Show 788 MR. A. SUTHERLAND ON THE [June 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 Schaefer's ' Physiology.' These will no doubt give an ultimate 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 published last year in 'Nature,' that those Orders which are structurally lowest,and therefore lowest in classification, are also lowest in temperature of all the mammals and form indubitably a chain of connecting-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. For to all animals there is a limit beyond which it is fatal to go. A frog will begin to collapse at 32° C. (90° F.). A man is normal at 37°, but begins to collapse at 41°, and is beyond the hope of recovery if his temperature reaches 42° (107°*6 F.). Birds iu general are normal about 42°, but perish at 45° (113° F.). The process of development, therefore, is to carry an animal up to that temperature at which 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, Omithorhynchus, being also the less 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 family carries us steadily up to the characteristic mammalian temperature. Having in a general way ascertained that this is the case 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 N e w Zealand, I have never seen one in Australia on which to make observations. But on visitino- London I received from Mr. Sclater and Mr. Bartlett courteous permission and a generous co-operation in taking the temperatures |