180 DR ALISONS OBSERVATIONS ON 



immediately present themselves, first, How are the cells themselves formed {e. g. 

 on the germinal membrane of the ovmn) out of a matter which is originally with- 

 out form, otherwise than by those very properties which are here ascribed to their 

 existence ? and, secondli/, If the properties are dependent only on forms, why do 

 they not exist in the dead state, Avhen the forms are, in many instances, still per- 

 fect ? The enunciation of these questions seems to me sufficient to shew, that 

 the correct expression of the state of our knowledge on this point is that already 

 quoted from Leibig, that the chemical forces in living bodies are subject, not 

 simply to an influence of forms, but to " the invisible cause hy which the forms of 

 organs are jrroduced" i. c, that we must include under the head of vital properties, 

 both the mechanical, or simply attractive power, by which cells or other organs 

 are formed out of amorphous matter, and likewise the chemical powers with 

 which these cells are endowed. 



It is no objection to what has been stated, of the strictly vital nature of these 

 chemical powers, to admit that their action is very often analogous to the principle 

 to which the name catcfli/sis is given by chemists, and which is exemplified likewise 

 in the chemistry of inorganic compounds, where the combination of two sub- 

 stances is determined by the presence of a third, which nevertheless takes no 

 part in the combination itself; or that it is analogous to that disturbance of the 

 equilibrum of chemical compounds, by which the fermentation of an organic com- 

 pound is transfeiTcd to another in contact with it, although the changes in the 

 two go on separately, and the compovmds formed are different. It is quite true, 

 that these modes of chemical action resemble and illustrate the manner in which 

 living solids, themselves undergoing continual changes of composition, determine 

 new arrangements of the elements of the compound fluids which are brought 

 in contact with them. But this analogy is far from being an explanation or 

 resolution of the one phenomenon into the other. In the fu-st place, the analogy 

 is essentially defective; because although it is true that in any living being, 

 already existing, different chemical compounds akeady exist in different parts of 

 the structure, which may act in these modes on the nourishing fluid, and deter- 

 mine distinct transformations of these at different parts ; yet this does not apply, 

 as already observed, to the first formation of each of the textures, at its appro- 

 priate point, from a homogeneous semi-fluid matter. But farther, although we 

 were to admit the analogy of all the chemical processes going on in living beings, 

 to these forms of simply chemical action, Ave should not thereby be authorised to 

 conclude that the vital processes have not that peculiarity which makes it in- 

 cumbent on us to regard them as a separate class. We say that the decomposi- 

 tion of carbonic acid, the combination of the carbon with the elements of water 

 to form starch, and the evolution of the oxygen, is a vital action, — not because it 

 is a change different in kind from the decomposition of water and evolution of the 

 hydrogen by iron and acid, — but simply because it indicates an affinity peculiar 

 to the state of life ; — because in no other circumstances, when the elements of 



