OF VITAL ACTIONS IN GENERAL. 39 



structure, or the loss of its distinguishing vital properties, is the result. 

 By the decomposition, which then takes place with increased rapidity, its 

 elements are restored to the Inorganic world ; presenting the very same 

 properties as they did when first withdrawn from it ; and becoming capa- 

 ble of being again employed, by any successive numbers of living beings, 

 to go through the same series of operations. 



42. Thus, then, we see that our fundamental idea of the properties' 

 of the simplest Living being consists in this ; that it has the capability 

 of drawing into its own substance certain of the elements furnished by 

 the inorganic world : that it forms these into new combinations (which 

 the chemist may find out methods of imitating) ; that it rearranges the 

 particles of these combinations, in that peculiar mode which we call or- 

 ganization ; that in producing this new arrangement, it renders them 

 capable of exhibiting a new set of properties, which we call vital, and 

 which are manifested by them, either as connected with the parent or- 

 ganism, or as appertaining to the germs of new structures, according to 

 the mode in which the materials are applied; that, notwithstanding its 

 peculiar condition, it remains subject to the ordinary laws of Chemistry, 

 and that decomposition of its structure is continually taking place ; 

 and finally, that the duration of its vital activity is limited; the changes 

 which the organic structure undergoes, in exhibiting its peculiar actions, 

 being such as to render it (after a longer or shorter continuance of 

 them) incapable of any longer performing them. 



43. There is abundant evidence, that the duration of the Life, or 

 state of Vital Activity, of an organized structure, is inversely propor- 

 tioned to the degree of that activity ; and consequently that Life is 

 shortened by an increased or abnormal activity ; whilst it may often 

 be prolonged by influences which diminish that activity. Thus, we shall 

 hereafter find reason to believe, that the duration of life in the Muscular 

 and Nervous tissues of Animals is entirely dependent upon the degree 

 in which they are exercised ; every call upon their activity causing the 

 death and disintegration of a certain part ; whilst if they be allowed to 

 remain in repose for a time, only that amount of decomposition will take 

 place, to which their chemical character renders them liable. Again, 

 we may trace the connexion between the vital activity of a part and the 

 duration of its life, by comparing the transitory existence of the leaves 

 of a Plant, which are its active organs of nutrition, with the comparative 

 permanence of its woody stem, the parts of which, when once completely 

 formed, undergo very little subsequent change. The most striking 

 manifestation of this connexion, however, is afforded by that condition, 

 in which, without any appreciable amount of vital activity or change, 

 an organized structure may remain unaltered for centuries ; not only 

 presenting at the end of that time its original structure, but being pre- 

 pared to go through its regular series of vital operations, as if these had 

 never been interrupted. This state may be designated as Dormant 

 Vitality. It differs, on the one hand, from Life; because Life is a 

 state of Activity. On the other hand, it differs from Death ; because 

 Death implies not merely a suspension of activity, but a total loss of 

 vital^ properties. Now in the state of Dormant vitality, the vital pro- 

 perties are retained ; but they are prevented from manifesting them- 



