19 
almost always open in the foetal state, and close 
after birth in land animals, is open through life in 
the beaver and sea otter, and other diving animals. 
The eustachian valve, which is remarkably strong in 
seals, is wanting in lions, bears, and dogs. Plants 
have not stomachs, but the mode in which roots 
universally absorb their liquid nutriment is ana- 
logous in operation to the similar absorption of 
nutriment by pores observed in zoophytes and cer- 
tain mollusca, in gorgoniz and teniz. The vessels 
of the stems of plants present striking analogies 
with the vascular or sanguiferous system of animals, 
adapting the greater number to live in air, many to 
live wholly in water. 
Nervous system. 
Animals are divided by Cuvier into two grand 
divisions. 1. Those with brain and spinal marrow, 
and a vertebral column. 2. Those without either. 
Of the former, the first class is mammalia. The 
preponderance of the brain above the rest of the 
nervous system is here most remarkable. “ The pro- 
portion of the spinal marrow to the brain in man 
(says Carus Y) I have found to be as 1 to 437: in a 
cat as 1 to 4: in a rat as 1 to 3: ina fish as 1 and 
a half to 1, the brain being least in quantity in the 
latter instance.” In this class the brain is one of the 
first organs to attain its full growth; and conse- 
Y Pag. 274. 
z A female brain, 43 ounces 6 drachms; male ditto, 41 ounces 
1 drachm. 
