186 METABOLIC HORMONES 



but the results reported have been contradictory. It is probable 

 that in physiological doses the cortical hormones cause no 

 significant change in the oxygen consumption oi normal 

 mammals. 



In hibernation the presence of active adrenal cortex seems to 

 be essential, in conjunction with relatively inactive thyroid glands. 

 It is therefore possible that cortical secretion helps to reduce 

 oxygen consumption in hibernating mammals, as it does in normal 

 frogs ; but the adrenal cortex is by no means the sole cause of all 

 the changes in metabolism and heat regulation that occur in 

 hibernation (Lyman and Chatfield, 1955). 



5.12 FAT METABOLISM 



Changes in fat stores in the body, like changes in respiration, 

 are often indicative of the general rate of metabolism, so that 

 increased fat consumption and decreased storage may accompany 

 increased oxygen consumption, and may be controlled by the 

 same hormone. Periodic changes in activity, such as moulting, 

 may be preceded by an increase in the rate of fat con- 

 sumption, and others, such as hibernation, by an increase in 

 fat storage. 



5.121 Increase in fat consumption or decrease in storage 



Crustacea. Fat consumption increases after the removal of a 

 moult-inhibiting factor in the sinus gland (§ 5.122) ; but, as yet, no 

 hormone or extract has been found that stimulates fat consump- 

 tion. It might be sought in the brain, v^hich yields an extract that 

 stimulates respiration (§ 5.111). 



Insecta. The presence of the corpora allata, with their 

 stimulating effect on the metabolic rate, tends to reduce the store 

 of fat in the fat bodies of most insects ; in adult females, when yolk 

 is being deposited in the ripening eggs, the corpora also facilitate 

 transport of fat to the ovary. This occurs in all insects except 

 in Bombyx, where the eggs are matured before the adult emerges, 

 and in Carausius. 



A detailed study of the production and transport of fat in the 

 grasshopper, Melanopliis dijferentialis^ shows that the corpora 



