7^ Appendix. 



which had passed through tubes heated to redness^ or enclosed 

 with air in hermetically sealed vessels, and exposed to boiling 

 water, becatfie the seat of infusorial life. ' ' 



The questions of life and its origin are problems which 

 science can never settle with certainty ; for like every thing re- 

 lating to force, as well as to intellect, they are to man profound 

 mysteries — belonging to a large extent, to the unknown and the 

 unknowable. Force, and the essence of life and of intellect, 

 not being visible to the eye — being beyond the power of the 

 chemist and the microscopist to discover, are not the subjects of 

 positive science. Each of them is the subject of inference only, 

 and of uncertain human reasoning. Hence the variety of opin- 

 ions upon such questions. But being matters of inference, from 

 the phenomena of nature and the action which we witness in the 

 universe, as well as from the consciousness which every person 

 has of the action and cognitions of his own mind, we have some 

 means of inquiring into the nature of such mysterious causes and 

 processes. 



To talk about molecules and protoplasm, molecular forces and 

 dynamical forces, throws no light upon the subject; but tends to 

 involve it in mysticism. 



By experiments and careful observation of natural phe- 

 nomena — of physical, vital, and intellectual action and their re- 

 sults, together with long study and inquiry into the causes of 

 such action and results, all our physical and metaphysical 

 sciences have been built up — including physiology and zoology, 

 botany and medicine, as well as physics and chemistry. Much 

 has been learned in relation to each and all of them — however 

 imperfect our knowledge may still be. Many theories more or 

 less false, but the most of them partially true, have been con- 

 ceived, generally received for a time, and then superseded by 

 others. And thus man has groped his way throngh darkness, to 

 the present state of human knowledge — often led astray by false 

 assumptions, and false theories — arising from erroneous inter, 

 pretations of the action of natural causes and of the elements of 

 nature. His inquiry into subjects which he can never master, 



