252 BIOLOGY. [Book ii. 



aliments ricli in fatty matters, exhale 1«RS carbonic acid, and, 

 consequently, burn more bydrogea. 



Tbe fewer tbe functions exercised by an inanitiated animal, 

 tbe less carbon it expends. This is the reason why Eidder and 

 Schmidt have observed that when animals were deprived of sight 

 the degree of their diurnal carbonic exhalation tended to equal 

 that of their nocturnal exhalation. 



Moleschott has shown that the action of light upon the sMn 

 notably augments the intensity of the respiratory phenomena, i 



During the day, under the influence of various kinds of 

 activity, the production of carbonic acid is, according to Schar- 

 ling, less by a quarter than during the nocturnal slumber. But 

 it is especially during the hibernal sleep that the absorption of 

 oxygen is reduced to its minimum. Regnault and Eeiset have 

 seen it fall to a twentieth part of what it was in a waking state. 



Contraction and muscular effort demand a large absorption of 

 oxygen, as Lavoisier and Seguin had already observed. This is 

 because, in a given weight of living matter, respiratory combus- 

 tion increases in direct proportion to the muscular activity. 



Behind every biological activity there is an oxydation of 

 the anatomical elements. No organ escapes this law, and the 

 nervous centres are as much in subjection to it as the other 

 organic apparatus. Every thought, every volition, every sen- 

 sation, corresponds to an oxydation of the living substance, as 

 well as every secretion, every movement, &c. 



In speaking of innervation, we shall have to consider, in con- 

 nection with it, the cerebral functionment. Lavoisier, after 

 having pointed out the relation which exists between muscular 

 activity and the exhalation of carbonic acid, wrote thus : " This 

 kind of observations leads us to compare the displays of force, 

 between which no connection would seem to exist. We may 

 know, for example, to how many potmds in weight the efforts of 

 a man reciting a discourse, of a musician playing an instrument 

 would correspond. We can even estimate how much there is of 

 ' Wiener Medidnische Wochenschrift, 185£. 



