MORBID POISONS. 371 



belong to the same class ; but although what heie takes place 

 exactly corresponds to the definition of life above assumed, no 

 unprejudiced mind would admit vitality in either process ; since 

 they are obviously chemical processes dependent upon the com- 

 mon chemical forces. 



The best definition of life involves something more than mere 

 reproduction, namely, the idea of an active power exercised by 

 virtue of a definite form, and production and generation in a 

 definite form. By chemical agency we shall some day be able 

 to produce the constituents of muscular fibre, skin, and hair ; but 

 we cannot form by their means an organized tissue, or an or- 

 ganic cell. 



The production of organs, the co-operation of a system of or- 

 gans, and their power not only to produce their component parts 

 from the food presented to them, but to generate themselves in their 

 original form and with all their properties, are characters be- 

 longing 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 pro- 

 duces. 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, mechanical 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 com- 

 plete cessation or reversal of their action. 



Such an influence and no other is exercised by the vital prin- 

 ciple over the chemical forces ; but in every case where com- 

 bination 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 

 impulse of motion or .change proceeds, it does not live. Its 



