PL4 
large surplus of carbon, however, s<ill en- 
ters the animal system through tlie medium 
of tlie lacteals, and continues to circulate 
with the chyle, or the blood, till it reaches 
the lungs. Here again a considerable por- 
tion of carbon is perpetually parted with 
upon every expiration, in the same form of 
carbonic gas, in consequence of its union 
with a part of the oxygen introduced into 
the lungs with every returning inspiration ; 
as is sufficienlly established by the experi- 
ments of Mr. Davy and other celebrated 
chemists ; while the excess, that yet re- 
mains, is carried otf by the skin, in conse- 
quence of its contact with atmospheric air; 
a fact put beyond all doubt by the experi- 
ments and observations of M. Jurine, al- 
though, on a superficial view, opposed by a 
few experiments of M. Ingenhouz ; and 
obvious to every one from the well-known 
circumstance, that the purest linen, upon 
the purest skin, in the purest atmosphere, 
soon becomes discoloured. In this way, 
then, and by this triple co operation of the 
stomach, the lungs, and the skin, vegetable 
matter, in its conversion into animal, parts 
with the whole of its excess of carbon. Its 
deficiency of azote becomes supplied in a 
twofold method. First, at the lungs ; also, 
by the process of respiration ; for we uni- 
formly find, and the experiments of Dr. 
Priestley and Mr. Davy are fully conclusive 
upon this subject, that a larger portion of 
azote is inhaled upon every inspiration, than 
is returned by every succeeding expiration ; 
in consequence of which, the portion re- 
tained in the lungs must enter into the sys- 
tem, in the same manner as the retained 
oxygen, and perhaps in conjunction with it ; 
while, in unison with this action of the 
Jungs, the skin also absorbs a considerable 
quantity of azote, 'and thus completes the 
-supply that is necessary for the animaliza- 
tion of vegetable food : evincing, hereby, 
3 double consent of action in these two or- 
gans, and giving us some insight into the 
mode by which insects and worms, which 
are totally destitute of lungs, are capable of 
employing the skin as a substitute for lungs, 
by breathing through certain spiracles in- 
troduced into the skin for this purpose, or 
merely through the common pores of the 
skin, without any such additional me- 
chanism. It is by this mode also that respi- 
ration takes place through the whole vege- 
table world, olfering us another instance of 
resemblance to many parts of the animal ; 
in consequence of which insects, worms, and 
the leaves of vegetables, equally perish, 
PLA 
by being smeared over with oil, or any other 
viscous fluid that obstructs their cutaneous 
orifices. 
“ But to complete the great circle of uni- 
versal action, and to preserve the important 
balance of nature in a state of equipoise, it 
is necessary, also, to inquire by what means 
animal matter is reconverted into vegetable; 
so as to afford to plants the same basis of 
nutriment which plants have previously af- 
forded to animals.” 
The process of putrefaction is shown to 
be'that principle, which is to be regarded 
as a most important link in the great chain 
of universal life and harmony. See Good's 
Oration. 
Corallines, madrepores, niillepores, and 
sponges, were formerly considered as fossil 
bodies ; but the experiments of Count Mar.- 
sigli evinced, that they are endued with 
life, and led him to class them with the 
maritime plants. And the observations of 
Ellis, Jussieu, and Peysonel, have since 
raised them to the rank of animals. The 
detection of error in long- established 
opinions concerning one branch of natnral 
knowledge, justifies the suspicion of its ex- 
istence in others which are nearly allied to 
it. And it will appear from the prosecu- 
tion of an enquiry into the instincts, spon- 
taneity, and self- moving power of vegetables, 
that the suspicion is not without foundation. 
PLANTAGO, in botany, plantain, a ge- 
nus of tlie Tetrandria Monogyiiia class and 
order. Natural order of Plantagiues, .Tiis- 
sieu. Essential character ; calyx four-cleft ; 
corolla four-cleft, with the border reflex; 
stamina very long; capsule two-celied, cut 
transversely. There are thirty-eight species. 
These plants, having little beauty, are rarely 
cultivated, except in botanic gardens. 
PLASHING of qnickset hedges, an ope- 
ration very necessary to promote the growth 
and continuance of old hedges. It is per- 
formed in this manner : the old stubs must 
be cut off, &c. within two or tliree indies 
of the ground, and the best and longest of 
the middle sized shoots must be left to lay 
down. Some of the strongest of these 
must also be left to answer the purpose of 
stakes. These are to be cut olF to the 
height at which the hedge is intended to be 
left ; and they are to stand at ten foot dis- 
tance one from another : when tliere are 
not proper shoots for these at the due dis- 
tances, their places must be supplied with 
common stakes of dead wood. 'The hedge 
is to be first thinned, by cutting away all 
but those shoots which are intended to be 
