34- Rev. P. Keith on the Conditions of Life. 



failure seems to be attributable, chiefly, to an unnecessary 

 effort at brevity, — brevis esse laboro, ohscuius fo, — perhaps it 

 might be worth our while to try the effect of a fuller enumera- 

 tion of particulars. What we lose in point and neatness, we 

 may gain in perspicuity ; and upon this principle I submit the 

 definition that follows: — Life is that attribute or energy of or- 

 ganized structures which renders them susceptible to impres- 

 sions, and enables them to discharge functions. It is real, or 

 it is potential : — real, if the energy is in operation ; as in the 

 case of an animal in motion, or of a plant protruding its buds 

 and blossoms ; — potential, if the energy is dormant, as in the 

 case of an egg not hatched ; or of a seed not sown ; or, as in 

 the case of the hybernation, whether of plants or animals. Life 

 originates in precedent life, and terminates in subsequent 

 death, which is an extinction of all vital functions, and of all 

 possibility of vital functions. — Taking this definition, with its 

 illustration, as our text, we proceed to remark that life in the 

 exhibition of its phaenomena always presupposes the existence 

 of certain peculiar conditions, previous, concomitant, or con- 

 sequent, without which it has never been known to manifest 

 itself, and of which the most essential are the following, — pa- 

 rentage, organization, aliment, aeration, temperature, death. 



Parentage. — There was a time in which philosophers be- 

 lieved in what was called the doctrine of equivocal generation 

 — that is generation springing from a fortuitous concourse of 

 atoms having an appetency to combine themselves into living 

 forms. This doctrine was taught and maintained by the most 

 celebrated philosophers of antiquity. Plants were regarded 

 by Diogenes as being generated from a mixture of earth and 

 putrid water; the water acting upon the earth, and moulding 

 it into form *. Plants whose seeds are not apparent were re- 

 garded by Theophrastus as being propagated by spontaneous 

 generation, because some tribes of animals were thought to 

 be so propagated + ; and parasitical plants were regarded as 

 springing from some corrupted matter generated on the tree 

 producing them J. The poets of antiquity had the same fic- 

 tions. Ovid replenishes his post-diluvian world with animals 

 that sprang up out of the earth sponte sua, excited by heat 

 and moisture §. The philosophy of the dark ages was not 

 likely to correct the errors of antiquity ; and when a better 

 philosophy was introduced, at the lime of the revival of learn- 

 ing, it could not be expected to correct them all at once. 

 Even Bacon, the great reformer of philosophical methods, 

 still gave his sanction to the doctrine of equivocal generation, 



* T/ieophr. Hi^i (pvrav iaTO(>ix;, lib. iii. 



"t" Ilfg/ (pvTui/ uiriau, lib, i. 



X Jbid. lib. V. § Metamorph. lib. i. 



as 



