82 MEANING OF ORDERS. 
tiles representing especially the muscular system, 
the Birds the nervous system, while in the Mam- 
malia the organs of the senses are most ‘highly 
developed. 
This theory, according to which there are as 
many great divisions or classes as there are 
structural systems or combinations of systems in 
the Animal Kingdom, seemed natural and signifi- 
cant, and there was something attractive in the 
idea that man represents, as it were, the syn- 
thetic combination of all these different systems. 
Oken also, in his exposition of his mode of 
classification, showed an insight into the struct- 
ure and relations of animals that commended it 
to the interest of all students of Nature, and én- 
titles him to their everlasting gratitude. Never- 
theless, his theory fails, when it is compared with 
facts. For instance, there are many Worms that 
have no respiration through the skin, while his 
appreciation of the whole class is founded on that 
feature ; and in his type representing circulation, 
the Mollusks, there are those that have no heart 
at all. 
It would carry me too far into scientific details, 
were I to explain all the points at which this 
celebrated classification fails. Suffice it to say, 
that there is no better proof of the discrepancy 
_ between the system and the facts than the con- 
stant changes in the different editions of Oken’s 
