214 THEORY OF THE CELLS. 
metabolic phenomena resides in that definite mode of arrange- 
ment of the molecules which occurs in crystals, combined with 
the capacity which the solution has to penetrate between these 
regularly deposited molecules (by means of which, presuming 
the molecules to possess polarity, a sort of galvanic pile will 
be formed), and that the same phenomena would be observed 
in an ordinary crystal, if it could be rendered capable of imhbi- 
bition. And then perhaps the differences of quality in the 
metabolic phenomena depend upon their chemical composition. 
In order to render tenable the hypothesis contained in the 
second point, it is merely necessary to show that crystals capable 
of imbibition can unite with one another according to certain 
laws. If at their first formation all crystals were isolated, if 
they held no relation whatever to each other, the view would 
leave entirely unexplained how the elementary parts of or- 
ganisms, that is, the crystals in question, become united to 
form a whole. It is therefore necessary to show that crystals 
do unite with each other according to certain laws, in order to 
perceive, at least, the possibility of their uniting also to form 
an organism, without the need of any further combining 
power. But there are many crystals in which a union of this 
kind, according to certain laws, is indisputable; imdeed they 
often form a whole, so like an organism in its entire form, 
that groups of crystals are known in common life by the names 
of flowers, trees, &c. I need only refer to the ice-flowers on the 
windows, or to the lead-tree, &e. In such instances a number 
of crystals arrange themselves in groups around others, which 
form an axis. If we consider the contact of each crystal with 
the surrounding fluid to be an indispensable condition to the 
growth of crystals which are not capable of imbibition, but that 
those which are capable of imbibition, in which the solution can 
penetrate whole layers of crystals, do not require this condition, 
we perceive that the similarity between organisms and these 
aggregations of crystals is as great as could be expected with 
such difference of substance. As most cells require for the 
production of their metabolic phenomena, not only their pe- 
culiar nutrient fluid, but also the access of oxygen and the 
power of exhaling carbonic acid, or vice versd ; so, on the other 
hand, organisms in which there is no circulation of respiratory 
fluid, or in which at least it is not sufficient, must be developed 
