11(S THE PHILOSOPHY 



pluir, by mepliitic air, or by remaining fome minutes under 

 water, the atStion of the heart ceafes. But, in many cafes of 

 this kind, the motion of the heart may, and frequently has 

 been renewed, by blowing air into the lungs, and by the ap- 

 plication of {Simulating fubftances to different organs of the 

 body. In perfons feemingly dead from a temporary fufpen- 

 iion of refpiration, if the lungs can be excited to a(ft, the mo- 

 tion of the heart inftantly commences, the circulation of the 

 blood is reftored, and life is recovered. This intimate con- 

 nection between refpiration and the adtion of the heart, is 

 one of thofe aftonifhing facts in the animal oeconomy, the 

 caufes of which v/ill perhaps forever elude the keeneft re- 

 fearches of the human intelledt. All we know is, that cer- 

 tain functions are indifpenlible to the exiftence of animals, 

 and that, if any of them are fufpended for a few feconds, 

 life is extinguiflied ; namely, the action of the brain and 

 nerves, the circulation of the blood, refpiration, and a pro- 

 bable refult of refpiration, animal heat. Thefe functions, 

 from their importance in the fyftem, have received the ap- 

 pellation of vital fun 8 ions. There are other functions of the 

 body, called natural, which are no lefs neceflfary to life, as 

 the digeftion and concoction of aliment, the various fecre- 

 tions and excretions. But they are diftinguifhed from the 

 vital functions, becaufe fome of them may be fufpended for 

 a conliderabie time without materially injuring the body. 



F.efpiration commences inftantly after birth, and is inftinc-^ 

 tively continued during life. In the foetus ftate, as formerly 

 mentioned*, refpiration is unnecelTary, becaufe the circula- 

 tion of the general mafs of blood is carried on through a dif- 

 ferent channel. In the a6t of infpiration, v/e are confclous 

 of making a certain effort ; but in the a6t of expiration we 

 fcarcely perceive any exertion whatever. 



* See above, page 66. 



