339 
PHYSIOLOGY, 
But, whether the fubftance contained in the nerves is 
exhausted by fenfations, or whether it merely undergoes 
an alteration in its chemical compofition, and becomes, 
as it were, neutralized, it mutt remain in the nerve 
throughout the whole of its courfe, and leave it only at 
one of its extremities. It does not, however, refemble 
the blood in the veflels, either as to the manner in which 
it is retained, or in which it moves in the nerve. There 
is no evidence of the nerves being tubular. No pheno¬ 
mena indicate that any matter elcapes from them when 
they are divided. Betides, what veflels could have pa- 
rietes fufficiently compact to retain fo fubtile a fluid as 
that of the nerves mull be. It is far more probable that it 
is retained in the nerves in the fame manner as the elec¬ 
tric matter is in eledlric bodies, by communication and 
infulation ; and that the nervous fyftem is its only con¬ 
ductor, while all the other parts of the animal body are, 
with refpedt to it, cohibent fubftances. 
The arrangement which Bichat has made of the phe¬ 
nomena of animated beings is worthy of particular notice 
in this place, becaufe the principle on which it is framed 
has been followed by nearly all fyftematic writers on 
phyliology, Blumenbach only excepted. We have feen 
that Haller’s mode of ftudying phyfiology was to begin 
with the Ample ftrudfures; to difplay their feparate or 
independent powers; and from the compound operation 
of thefe powers to deduce the general phenomena of life. 
The French phyfiologifts, on the other hand, begin by 
defining life to be a mere abftradl expreflion, meaning the 
totality of the functions. This definition they have prided 
themfelves much upon; and have derided us with no 
lenient hand, becaufe fome of our eminent writers have 
attempted to advance a ftep further, and atk the caufe of 
thofe functions. It mull be confefl'ed that it would have 
been better had a more complete knowledge of funflions 
preceded the enquiry into potver; but (till it mult be very 
obvious, that the natural tendency of our minds is 
towards this enquiry, and that it is a legitimate one, provi¬ 
ded we avoid that quickfand, the nature of ultimate caufes. 
Whether Bichat did or did not advance our knowledge 
of phyfiology by his famous arrangement, he certainly 
has the merit of an ingenious artificial fcale on which he 
has defcribed in a memorable form a number of facts 
both original and borrowed. But this will be more 
clearly feen by the following analyfis of his method. 
Having, as we have feen, defined life to be a Ample re- 
fult of unknown and unknowable powers, this author 
divides it into two clafi'es, an animal and an organic life. 
The one is common to vegetables and animals; the 
other peculiar to the latter. “ Compare together (fays 
he) two individuals, one taken from each of thefe king¬ 
doms-: one exifts only within itfelf, has no other rela¬ 
tions to furrounding objefts-than thofe of nutrition; is 
born, grows, and perifhes, attached to the foil, which re¬ 
ceived its germ : the other joins to this internal life, 
which it poflefles in a ftill higher degree, an external life, 
which eftabliflies numerous relations between it and the 
neighbouring objects, unites its exiftence to that of other 
beings, and draws it near to or removes it from them ac¬ 
cording to its wants or fears. We might fay that the ve¬ 
getable is the fkeleton of the animal; and that, in order 
to form the latter, it was.only neceflary to clothe the fkeie- 
ton with an apparatus of external organs, calculated to 
eftablith the neceflary relations. Hence it follows that 
the funClions of the animal form two very diftinCt claffes. 
One of thefe confifts of. an habitual fucceflion of aflimila- 
tion and excretion ; by which it is conftantly transform¬ 
ing into its own lubftance the particles of other bodies, 
and then rejedling them when they have become ufelefs. 
By the other he perceives furrounding objedfs, reflects on 
his fenfations, performs voluntary motions under their 
influence, and generally can communicate, by the voice, 
his pleafures or pains, his defires or fears. By the one 
he lives only within himfelf; by the other be carries his 
exiftence out of the fphere of his own body. 
“ I call the functions of the former clafs, taken all to¬ 
gether, the organic life, becaufe all organifed beings, whe¬ 
ther vegetable or animal, enjoy it in a more or lei's 
marked degree, and becaufe organic ftrudiure is the only 
condition neceflary for its exercife. The aifembled func¬ 
tions of the fecond clafs form the animal life, fo named 
becaufe it is the exclufive attribute of the animal king¬ 
dom.” 
Generation does not enter into the feries of phenomena 
of thefe two lives, which relate entirely to the individual; 
W’hile that fundlion regards the fpecies, and is confe- 
quently connedfed only in an indirect manner to molt of 
the other functions. Its exercife does not begin until 
the others have been for a long time in action ; and it is 
extinguilhed long before they ceafe. In molt animals its 
periods of adfivity are feparated by long intervals of en¬ 
tire inadfion : and in man, where the renditions are lefs 
durable, its relations to the other fundtions are not more 
numerous. 
Each of the lives is compofed of two orders of func¬ 
tions, fucceeding each other, and mutually connected. 
In the animal life, thefirft order takes place from the ex¬ 
terior of the body to the brain ; and the fecond, from the 
latter organ to thofe of locomotion and the voice. Ob- 
jedls affiedt fuccefiively the fenfes, the nerves, and the 
brain. The firft receive, the fecond tranfmit, and the lalt 
perceives, that impreflion which conftitutes a fenfation. 
The animal is nearly pafiive in this firft order of fundtions; 
he becomes adtive in the fecond, which refults from the 
fucceflive operations of the brain, where volition arifes 
in confequence of fenfation, of the nerves which tranf¬ 
mit this volition, and of the locomotive and vocal organs, 
which are the agents of its execution. A double move¬ 
ment of compofition and decompofition exifts alfo in the 
organic life. Hence the animal is not the fame at one 
time as at another : his organization is unchanged, but 
the component elements are conftantly varying. The or¬ 
der of fundtions, which afiimilate to the animal nutritive 
fubftances, confifts of digeftion, circulation, refpiration, 
and nutrition, AH foreign matters undergo the influence 
of thefe four fundtions, before they belong to the elements 
of the body. After a certain time ablorption removes 
them, and conveys them into the circulation, from which 
they are feparated by the cutaneous or pulmonary exhala¬ 
tion, or by the various lecretions. Thus ' abforption, 
circulation, exhalation, and fecretion, form the fecond 
order of fundtions in the organic life; or the order op- 
pofed to aflimilation. The circulating fyftem is the 
common centre in the organic, as the brain is in the ani¬ 
mal, life. The blood confifts of two parts; one, furnifhed 
principally by the food, affords the materials of nutrition ; 
while the other, conftituting the wreck or refidue of all 
the organs, fupplies with materials the fecretions and 
external exhalations. Yet the latter fundtions fometimes 
convey out of the body the produdts of digeftion where 
they have never been employed in nouriihing the organs. 
This is exemplified in the urinary and cutaneous difehar- 
ges conlequent on copious drinking. 
The moft eflential difference that appears to exift be¬ 
tween the organs of the animal and thole of the organic 
life, is the fymmetry of the one, and the irregularity of 
the other. This obfervation, indeed, does not apply to 
all animals; nor is it invariably true in man; but it 
holds good generally in the latter, and forms a ftriking 
general feature. Two globes exadfly alike receive the 
impreflion of light. Sounds and odours have each their 
double organ. The median line is clearly marked on the 
tongue, and its two halves exadfly refemble each other. 
This line is not very manifeft in the fkin. The nerves, 
which tranfmit impreflions from the fenfitive organs, are 
arranged in fymmetrical pairs. And the brain, in which 
the impreflion is received, has a regular form; its double 
-parts refemble each other on the oppofite fides; and its 
Angle organs are alt fyrnmetrically divided by the median 
line into two exadflv-correfponding halves. The nerves, 
which 
