REGULATION OF THE BODY'S TEMPERATURE 409 



the augmented respiration appearing with a high external temperature (page 

 318) is caused by a direct exciting effect of the blood, for it can be reproduced 

 in all its essential features by locally warming the blood in the carotids on the 

 way to the brain; but it will not appear, notwithstanding a very strong heat 

 stimulus, when the head is cooled. 



The ability to maintain a constant temperature in certain species of ani- 

 mals, including man, is not fully developed immediately after birth. In such 

 warm-blooded animals as have a well-developed nervous system at birth 

 e. g., guinea pig and chick the heat-regulating mechanism also is completely 

 functional at this time. But those which, like rats and pigeons, are born 

 blind and helpless, only acquire the power of regulating their own temperature 

 in the course of the second week (Pembrey). The newborn child also has 

 not yet come into full possession of its power to regulate its heat (Raudnitz). 

 It is probable that this post-embryonic development of the regulatory mech- 

 anism is intimately connected with the development of the neuromuscular 

 apparatus going on at the same time. 



