492 THE KESPIRATORY EXCHANGE 



ment of the chick within the egg, but it is necessary to remember 

 that the output of carbon dioxide and the intake of oxygen for 

 the conventional terms of one kilogram of body-weight and 

 one hour must be calculated not from the weight of the egg but 

 from the weight of the embryo contained therein. Thus on the 

 nineteenth day of incubation the carbon dioxide discharged by 

 an egg ( 9 ) was '007 grm. in 15 minutes at a temperature of 40 ; the 

 weight of the egg after the shell was removed^was 52 grm. ; that 

 of the embryo without its yolk-sac 27*5 grm. The discharge of 

 carbon dioxide per kilogram of body-weight and one hour is thus 

 almost exactly 1 grm. A first-day chick discharged 1-714 grm. per 

 kilo and hour at a temperature of 37*75, and 3-606 grm. at 17, a 

 value which much exceeds that obtained by Regnault and Reiset 

 for a hen, namely, 1-327 grm. at 19. 



In the case of the newly born animal and infant, determinations 

 show that the respiratory exchange is under natural conditions 

 more energetic than in the adult ; it is easily influenced by changes 

 of external temperature, for the regulation of temperature is im- 

 perfect, and it will be shown later that in many cases cold will 

 produce a marked fall in the respiratory exchange of the newly 

 born. Against this effect there are natural safeguards ; the 

 breeding season generally begins in the spring, and the young 

 are produced when the weather is mild ; the mother selects a 

 sheltered spot for her nest or bed and broods over her helpless 

 offspring. Warmth is necessary and warmth is secured ; the care 

 of the mother is not for the relief of weakness due to parturition, 

 for such weakness is obviously not present in birds and is also 

 absent in woman and mammals untouched by the degenerating 

 influence of over-civilisation and domestication ; moreover, this 

 parental care is seen in many cock-birds, which share the duties 

 of incubation and brooding with the hen. The degenerates of 

 modern society have degraded maternity from its position as the 

 highest duty, and too often the woman of society either cannot 

 suckle her offspring or has lost the imperative natural instincts 

 of cherishing her infant with the warmth of her body and feeding 

 it with her own milk. 



Under favourable conditions the infant's respiratory exchange 

 is most active. Thus Babak ( 10 ) found that in an infant 1 J hours 

 old and weighing 2670 grm. the intake of oxygen and output 

 of carbon dioxide were 552 c.c. and 368 c.c. per kilo and hour ; 



