224 ZOOLOGICAL PHILOSOPHY 



Animals breathing with lungs undergo alternate swelhngs and con- 

 tractions of the cavity containing their respiratory organ. Now these 

 movements are carried out with greater or less facility, according 

 as the orgasm of the supple parts is more or less energetic. Thus 

 several mammals, such as the marmot and dormouse, and many 

 reptiles, as the snakes, fall into a torpid state on certain reductions of 

 temperature, because they then have a greatly weakened orgasm, 

 from which results secondarily a slackening of all their organic fimctions 

 including that of respiration. 



If this dechne in the energy of their orgasm did not take place, there 

 would be no reason why any less air should be breathed by these animals 

 when it is cold. In bees and ants which breathe by tracheae and 

 undergo no alternative swellings and contractions, it cannot be said 

 that they breathe less when it is cold ; but there are sound reasons 

 for the behef that their orgasm is then greatly enfeebled, and thus 

 accounts for the torpid state which they undergo in these conditions. 



Finally, in warm-blooded animals their internal heat is almost 

 entirely produced within their bodies, either as a result of the decom- 

 position of air in respiration as is generally held, or because it is con- 

 stantly given off from the arterial blood while changing into venous 

 blood, as I myself beUeve ; in either case the orgasm gains or loses 

 energy, according as the internal caloric increases or diminishes in 

 quantity. 



As regards the explanation which I am giving of orgasm, it is a matter 

 of indifference whether the caloric produced in the interior of warm- 

 blooded animals, is the result of the decomposition of air in respiration 

 or is an emanation from the arterial blood as it changes into venous 

 blood. If, however, it is desired to consider this question, I should 

 put forward the following suggestions : 



If you drink a glass of spirits, the resulting warmth that you feel 

 in your stomach assuredly does not spring from increased respiration. 

 Now if caloric may be given forth from this hquor as it undergoes 

 changes in your organ, so too it may be exhaled from your blood 

 when it undergoes changes in its component parts. 



In fever when the internal heat is greatly increased, it is observed 

 that respiration is also faster, and hence it is inferred that the con- 

 sumption of air is greater. This supports the view that the internal 

 caloric of warm-blooded animals results from the decomposition of 

 the respired air. I know of no experiment to show definitely whether 

 the consumption of air during fever is really greater than in health. 

 I doubt whether it is so ; for if respiration were faster in this diseased 

 condition it may be compensated for by each inspiration being less, 

 owing to the constraint of the parts. What I do know is that when 



