656 FUNCTIONS OF ANIMALS. 



and unfit for the use of the animal ; a new bone, therefore, is 

 formed in its place, and the old one is carried off by the absor- 

 bents. In order to form this new bone, large quantities of phos- 

 phate of lime are deposited in a place where the same quantity 

 was not before necessary. Now, who informs this agent that an 

 unusual quantity of phosphate of lime is necessary, and that it 

 must be carried to that particular place ? Or, granting, as is 

 most probable, that the phosphate of lime of the old bone is 

 partly employed for this purpose, who taught this agent that the 

 old bone must be carried off, new-modelled, and deposited and 

 assimilated anew ? The same wonders take place during the heal- 

 ing of every wound, and the renewing of every diseased part. 



But neither in this case is the power of this agent over the 

 chemical agents which are employed absolute. We may prevent 

 a fractured bone from healing, by giving the patient large quan- 

 tities of acids. And unless the materials for new- wan ted sub- 

 stances be supplied by the food, they cannot in many cases be 

 formed at all. Thus the canary bird cannot complete her eggs 

 unless she be furnished with lime. 



As this agent which characterizes living bodies does not ap- 

 pear to act according to the principles of chemistry, any inquiry 

 into its nature would be foreign to the subject of this work. 

 Physiologists have given it the name of the living or animal 

 principle ; and to them I beg leave to refer the reader. 



Besides the different organs of the body, the blood is also em- 

 ployed in forming all the different secretions which are necessary 

 for the purposes of the animal economy. These have been enu- 

 merated in a former part of this work. The process is similar to 

 that of assimilation, and undoubtedly the agents in both cases 

 are the same ; but we are equally ignorant of the precise man- 

 ner in which secretion is performed as we are of assimilation. 



After these functions have gone on for a certain time, which 

 is longer or shorter according to the nature of the animal, the 

 body gradually decays, at last all its functions cease completely, 

 and the animal dies. The cause of this must appear very extra- 

 ordinary, when we consider the power which the animal has of 

 renewing decayed parts ; for it cannot be doubted that death pro- 

 ceeds, in most cases at least, from the body becoming incapable 

 of performing its functions. But if we consider that this power 

 is limited, and that it must cease altogether when those parts of 



