267 



it can do no more, it has no virtue to be what it is not. But 

 causes have relations by which they join their existence, and each 

 being a different form, their distinction is lost in this union, at 

 least to our perception. The study of these relations forms the 

 principal business of philosophy ; and as knowledge of individual 

 causes must precede the steps by which we investigate their rela- 

 tions, hence the complication which in this our present subject 

 belongs to the analysis of the causes upon which phenomena depend. 

 We are professedly ignorant of the most essential of these causes: 

 and where this particular knowledge is denied us, we can only 

 state our difficulty, and, with a view to future progress, shew its 

 conformity with those general principles which must direct our 

 research in this, as well as in all other instances. 



22. If a gelatinous bed is converted into muscular fibres, if 

 cartilage is converted into bone, if the amazing structures of a per- 

 fect animal are developed to this state from a nucleus to all ap- 

 pearances without a character, if in the course of being new 

 functions arise, if the functions which maintain this fabric become 

 disordered and finally cease, and this piece of anatomy fall to 

 decay, we can regard this series as the result only of properties 

 and relations which are disposed/or progressive change. 



23. Progressive change is accomplished by reiterated causa- 

 tion. If a thing preserve an uniform identity, it does so because it 

 is surrounded by no agents which are so related with as to affect 

 it ; if a thing is once changed, and then preserve its new form, it is 

 that it is exposed to the operation of a related agent, and that the 

 form which it assumes in consequence ceases to be related with the 

 existences which surround it ; if a thing suffers one change and 

 then another, and a third, through a lengthened, series* it is because 

 each successive form of existence has a caus,ative relation with 

 Other forms. 



24. To apply these principles first to our physiology. Pro- 

 perties are related with a nutrient material containing infinite con- 

 stituents, so as to separate or produce from it a gelatinous fluid; 

 the properties which produced this fluid belong to the organic 

 spirit, and constitute one state, of it; this state is a form of 

 existence which is related with surrounding agents, so as to suffer 

 a change; this new condition is again related with other constitu- 

 ents of the material, and the end of this new relation, thus esta- 

 blished, is, that the properties producing jelly, having changed 

 their state, cease to separate this fluid, and produce, conformably 

 with their present or new state, the aggregation perhaps of carti- 

 lage. These processes are repeated, and cartilage gives place to 

 bone, and so of all the other structures. 



25. But we observe in.stan.cea wherein thjs progression ap- 

 pears to be interrupted : the subject or t,he particular effect which 

 we contemplate appears for a time to be at rest, and then at per- 

 haps a distant period it assumes a change. We may trace the 

 stages of conversion in the .growth of the fetus, and we can 



