s 
REVIEW OF CERTAIN DOCTRINES 
this idea, that he proceeds to make the following remark : 
" This law, of which the simplest expression is that were two 
chemical substances are in contact any motion occurring among 
the particles of the one, may he communicated to the other, is of 
a more purely mechanical nature than any other principle yet 
received in chemistry, and, when more definitely established by 
succeeding researches, may be the basis of a dynamic theory in 
chemistry, as the law of equivalents and multiple combination 
expresses the statical condition of bodies which unite by chemical 
forced 
I perfectly agree in opinion with the author of these sug- 
gestions, as to the purity of the mechanical attributes of 
the principle on which they are founded, but cannot on 
this very account deem them competent to explain the 
chemical phenomena on which he conceives them to bear. 
As the mechanical influence of the motion of bodies is as 
the weight multiplied by the velocity, is it conceivable that 
any movement in the particles of one part, by weight, of 
diastase, can be productive of analogous movements in 
two thousand parts of starch ? 
The idea that yeast might owe its power to animalcules, 
suggested itself to me more than thirty years ago, and seems 
to have some support from the fact, that fermentation only 
thrives within the range of temperature compatible with 
animal life. Latterly, its activity has been ascribed by some 
observers to the agency of extremely minute vegetables. 
Kane, while admitting the existence in yeast of " a vast 
number of globular bodies, possibly animalcules" treats 
the idea as untenable, because the weight of the alcohol 
and carbonic acid is greater than that of the sugar employ- 
ed. But if the union of water with the elements of the 
sugar can add to the weight of the products without the 
assistance of animalcules, wherefore should their agency 
be inconsistent with an augmentation from the same source? 
It seems to be overlooked that there has been much reason 
to infer, that the conversion of cane sugar into grape sugar 
