1854.] OF THE ROYAL INSTITUTION. 415 
whose universal presence in the plant seemed to offer the best prac- 
tical chemical test ; but Busk and other observers had recently de- 
tected this substance in the brain of man, and there was reason to 
suppose that starch might be very generally present in the ani- 
mal kingdom. 
It was thus seen that no one point in structure or chemical com- 
position could furnish a means of distinction. A physiological point 
of much interest and importance had principally determined a certain 
number of botanists in claiming the Diatomacee and Desmidee as 
plants. In certain conferve it had been observed, that previous to the 
production of the zoospore, two contiguous cells united, and each con- 
tributed its contents to form the germinating spore. This process 
was observed by Ralf and others in Desmidee, and subsequently by 
Thwaites in the Diatomacee. In addition to this point these families 
exhibit other relations with the vegetable kingdom. 
Whatever might be the difficulties presented in any individual case 
in the application of all or any of the before-mentioned distinctions, 
there was evidently a great antagonism or polarity exhibited by the 
animal and vegetable kingdoms when viewed as a whole. They 
were mutually dependent, attained the same ends in their growth 
and organization, but by contrary means. The great function of 
the animal tissues was the absorption of oxygen, and the disengage- 
ment of carbonic acid. The great function of the vegetable tissues 
was the absorption of carbonic acid and the disengagement of 
oxygen. The processes in the history of the life of the two king- 
doms in which these distinctive functions appeared to be reversed, 
were not exceptions to the law, but were due to other agencies 
than those connected with the essential life of the plant or the 
animal. Thus carbonic acid was given out by plants at night, 
during fructification and germination. In the first instance, the 
gas given out was that which had been taken up during the day, 
and was not decomposed by the agency of light. In the latter 
instances a process of exudation took place in which the contents of 
the cells were undergoing change independent of the life of the plant. 
The germ during the growth of its cells absorbed carbonic acid and 
gave out oxygen, as in the growth of all other vegetable cells. The 
development of the carbonic acid arose from the decomposition of 
the starch and the sugar of the albumen of the seed. In the cases 
where animals had been found to give off oxygen, it was doubtful 
as to whether plants were not present or even mistaken for ani- 
malcules. 
The composition of a series of vegetable and animal products was 
exhibited ; and attention was drawn to the fact, that in all cases the 
vegetable compounds were formed from carbonic acid and water, 
or from carbonic acid, water, and ammonia, by the loss of oxygen. 
Acetic acid was referred to as an exceptional instance; but it was 
shewn that it was more probable, where acetic acid occurred as the 
result of vegetation, that it occurred as the result of deoxidation 
