176 



METABOLIC HORMONES 



that increased respiration can also be obtained in adult salamanders 

 by thyroid injection (Taylor, 1939) shows that the action is not 

 merely a reflection of the stimulus towards metamorphosis in the 

 larval forms (cf. Part II, § 3), as might otherwise be supposed. 



140 

 120 

 100 

 80 



Control 6 onimals 



"Respiratory quotient" 

 .Oxygen consumption 



Ttiyroxine 5 animals 



140 



I 2 3 4 5 6 7 



Mammalian ttiyroid 2 animals 



10-14 



10-14 



12 3 4 5 



No. of days after injection 



10-14 



Fig. 5-4. Effects of thyroxine and thyroid extracts on the oxygen 

 consumption (full line) and respiratory quotient (as percentages 

 of the average values for the controls, shown by broken line) in 

 male w^hite rats, Rattus. Time in days as abscissae. The effects of 

 purified thyroxine and the extract of a mammalian thyroid are 

 similar. The extract of parrot fish, Pseudoscarus, thyroid causes less 

 increase in oxygen consumption, but the effect lasts longer than the 

 others (from D. C. Smith and Brown, 1952). 



