THEIR MODE OF ACTION. 355 



system of organs, and their power not only to 

 produce their component parts from the food pre- 

 sented to them, but to generate themselves in their 

 original form and with all their properties,, are cha- 

 racters belonging exclusively to organic life ; and 

 constitute a form of reproduction independent of 

 chemical powers. 



The chemical forces are subject to the invisible 

 cause by which this form is produced. Of the 

 existence of this cause itself we are made aware 

 only by the phenomena which it produces. Its 

 laws must be investigated just as we investigate 

 those of the other powers which effect motion and 

 changes in matter. 



The chemical forces are subordinate to this cause 

 of life, just as they are to electricity, heat, mecha- 

 nical motion and friction. By the influence of the 

 latter forces, they suffer changes in their direction, 

 an increase or diminution of their intensity, or a 

 complete cessation or reversal of their action. 



Such an influence and no other is exercised by 

 the vital principle over the chemical forces ; but in 

 every case where combination or decomposition 

 takes place, chemical affinity and cohesion are in 

 action. 



The vital principle is only known to us through 

 the peculiar form of its instruments, that is, through 

 the organs in which it resides. Hence, whatever 

 kind of energy a substance may possess, if it is 

 amorphous and destitute of organs from which the 



A A2 



