Respiration and Metaholisni 



261 



The ability of diving mammals to remain submerged is, then, based on 

 several interacting factors, with anaerobic glycol^'sis and tolerance to high 

 levels of lactic acid and carbon dioxide playing critical roles. 



Effect of Temperature on Breathing. In strictly homoiothermic forms there 

 is little change in breathing rate at rest over a fairly wide range of external 

 temperature. However, at both the high and low limits of normal temperature 

 control respiratory movements may increase severely. The respiratory center of 

 birds and mammals itself is sensitive to changes in blood temperature, and 

 both the depth and rate of respiration increase with high body temperatures. 

 In the wren, Troglodytes, with a normal body temperature range of 100° to 

 107° F., the breathing rate increases from an average normal of 100 per minute 

 at 105° F. to 340 per minute at 1 16° F.^^ Likewise a severe reduction in body 

 temperature in this small bird may produce a ventilation rate of 240 per 

 minute. The respiratory center of the bat is likewise sensitive to thermal stimu- 

 lation. -"^"'^ 



Among invertebrates and cold-blooded vertebrates the temperature eflFects 

 on breathing largely parallel those on oxygen consumption— there is an increase 

 in activity at high temperatures (Fig. 60). ^^' '^"^^ ^^'^ 



100 



60 



60 



40 



20 



1 ^! 



11-3^ 



R 



\z 



14 



16 

 Temp. 



18 



'C. 



20 



IZ 



Fig. 60. Effect of temperature on respiration of the puffer fish, Spheroides. R, respira- 

 tion per minute. M, cc. Oj/kg./hr. W, dl. H-O/hr. pumped through branchial cavity. 

 O, percentage of O,' utiHzed. From Hall."" 



Respiratory Movements During Flight. Wing beat and breathing move- 

 ments may be synchronized during flight, as in insects, birds, and bats,-"'- -^•^• 

 :io.T. :iS5 bm respiratory movements may stop altogether during flight (Fig. 

 61).^^" The finch, Fringilla, has a respiratory rhythm of 4-5 per second both 

 at rest and in flight, and superimposed on this a flight rhythm of 15-20 per 

 second."'^ The actual respiratory advantage of synchronized movement is not 

 clear, but in those instances in which flight movements greatly augment respira- 

 tory rhvthms a distinct benefit may be derived. 



