ON THE VETERINARY MATERIA MEDICA. 49 
This contractility, independent of sensation, was then shewn 
by the effect of galvanism on a rabbit just killed; and even 
on a limb separated from the body. Not the slightest was per¬ 
ceived when the fluid was directed through a vigorous plant. 
Similar and stronger motions were observed in the Chinese 
leaf, and different substances on the Electrophorus, where life did 
not exist. They were mere mechanical actions. 
The chemical composition of animal and vegetable substances 
materially differed. The essential elements of organized matter 
were, carbon, oxygen, hydrogen, nitrogen, and some alkaline and 
earthy salts, variously combined. In vegetables, one of the most 
important of these elements was wanting: plants did not contain 
the minutest quantity of nitrogen. 
In their decomposition the results were strikingly different. 
Vegetables abounding with oxygen, have a tendency, after death, 
to become acid—by new combinations with carbon and hydrogen. 
The soft parts of animals were disposed to become alkaline : the 
nitrogen entered into a new combination with the hydrogen, and 
formed ammonia. The geologist had availed himself of this, and 
could distinguish a vegetable from an animal fossil, by the odour 
which proceeds from them in the act of burning. Shewn. 
The principal organs of the plant were the root —by which 
it was attached to the soil, and through which it derived its prin¬ 
cipal nutriment. The root consisted of the body or caudex, and 
the rootlets. The rootlets terminated in extremely minute fibrils. 
They were the vessels which took up the nutriment, consisting 
either of water, or vegetable or animal substances undergoing 
various states of decomposition, and conveyed it to the caudex. 
This was a kind of reservoir, in which a portion of it was hoarded 
up, and probably underwent important changes. Before the carrot 
begins to flower, a portion of the sap or proper juice is accumulated 
in the root, and the vegetable is esculent. When the grand pur¬ 
pose of reproduction is accomplishing, the root parts with its fluid 
contents, and becomes a mass of fibres, on which our masticating 
organs can make no impression. When the seed is ripened, and 
the continuance of the species provided for, the sap once more 
descends to the root, and accumulates there, and the root again 
becomes soft, and sweet and nutritive. This will explain many 
circumstances connected with our esculent vegetables, and guide 
us in the cultivation of them. 
From the root proceeds the stem —that which either supports 
the plant, or conveys the sap to the branches. It differs in dif¬ 
ferent plants, from the creeping bramble to the palm 100 feet in 
height, and from the scirpus capillaris, not exceeding the bulk of 
a hair, to the calibash twenty-seven yards in circumference. 
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