fii 



24 



THE BEGINNINGS OF LIFE. 



ment) 



Lavoisier 



su 



bstances 



broi 



w 



ithin 



the bloc 



the animars nature and the necessities of its existence 

 compel it to manifest. Animals display^ in varying 

 proportions^ three principal modes of vital activity 

 which testify to the continual liberation of force within 

 them :— (i) they appear to produce heat; (2) they move 

 by reason of the contractility of certain tissues; and 

 (3) they display certain nervous phenomena. 



I. Very many animals constantly maintain them- 

 selves at a temperature above that of the medium in 

 which they live; this being more especially the case 

 with the so-called ^arm-bkoded animals — amongst whidi 

 birds are most remarkable for the very great difference 

 existing between their temperature and that of the air, 

 The cause of this difference in temperature between 



r 



the animal and its medium has been variously explained 

 at different times. It was believed by Galen that heat 

 was actually produced de novo in the left ventricle of 

 the heart • and even John Hunter thought that the pro- 

 duction of animal heat depended upon a special vital 

 force or principle, which was able not only to produce 

 but actually to destroy heat. Others — and that even 

 in comparatively, recent times — have striven to prove , tions (tf carbo 

 that some principle resident in the nervous system 



with all the rii 

 that the oxygen 

 attacks the org 

 burns them, c( 

 hydrogen to for: 

 that this slow 

 the blood is ar 

 then instituted 

 of heat abstra( 

 contact with ai 

 surface of the 

 the quantity of 



was 





combination o 

 capable of giving rise to animal heat. The true theo- | bloody and th 

 ries on this subject, however, may be said to date as I engage,} 4^; 



*'«»«, he 

 '*«««^ car, 



far back as the close of the eighteenth century, and to 



i 



have commenced with the brilliant discoveries of Lavoi 

 sier. Speaking of his researches^ M. Gavarret says^*. 



^ Loc. cit. p. 99. 



\ 



1 i 



