4 8 THE STRUCTURE AND LIFE OF BIRDS chap. 



of which I shall speak soon. But these also may have 

 been to some extent warm-blooded. 



The fact that existing reptiles are cold-blooded, 

 while birds have high temperatures, is really no barrier 

 between the two classes. There was once a Python 

 at the Zoological Gardens which laid eggs, and for 

 six weeks sat upon them, at the end of which time 

 they were addled, or, at any rate, the young snakes 

 in them were dead. 1 But the python had not " sat " 

 in vain, for every day her temperature was taken by 

 experts, and also that of a male python hard by who 

 was subjected to the same cpnditions. The female had 

 an average temperature of 89-07° F., the male of 

 86-03° F. The maximum temperatures were for the 

 female 92-8° R, for the male 89-8°. But the great 

 difference between warm and cold-blooded animals 

 is that the former do not change their temperature 

 as that of the air changes. The female python was 

 once 16-7° warmer than the surrounding air, the male 

 never more than 1 1 -6°. In a similar case observed in the 

 Jardin des Plantes in 1861 the female's temperature 

 once rose 38-7° F. above that of her surroundings. She- 

 pythons, therefore, when incubating are not altogether 

 the sport of atmospheric changes. Even in mammals 

 temperature varies very much, the small ones having 

 as a rule the hottest blood. Those of large bulk 

 range between 97^° and 98!°. The sheep is said to 

 have a temperature of 104°. The Echidna sends the 

 thermometer only to 82 1°, and the Ornithorhyncus 

 only to 76 f. In birds the range is considerable, 



1 Proceedings of the Zoological Society, 1 881, "The Incubating 

 Python," by W. A. Forbes. 



