PHYSIOLOGY. 
340 
which tranfmit our volitions from the brain to the agents 
of locomotion and the voice; and the locomotive organs, 
compofed of a great part of the mufcular fyftem, of the 
bony fyftem audits dependencies; and the larynx and its 
accefl'ory organs; the double agents for the execution of 
volitions; have a fymmetrical ftru6ture throughout. 
The mufcles and nerves, when they do not belong to 
the animal life, no longer exhibit this regularity of 
form. The heart, and the mufcular coverings of the 
digeftive vifcera, prove this with refpect to the mufcles; 
and the great fympathetic nerve, every-where employed 
in the internal life, clearly Ihows the irregularity in the 
nerves. 
On furveying the parts concerned in the organic life, 
we lha.ll find that an exactly oppofite character is appli¬ 
cable to them. The ftomach, the inteftines, the fpleen, 
liver, Sec. are all irregularly formed in the digeftive fyf- 
tem. In the circulating apparatus, the heart, and the 
large veflels, fuch as the venae cavae, the azygos, the 
vena portarum, &c. exhibit no trace of fymmetry. Con¬ 
tinual varieties are obferved in the blood-veffels of the 
extremities, and the difpofition of one fide is often by no 
means the fame with that of the other. 
The refpiratory apparatus, at the firft glance, appears 
regular; but we find the two branches of the trachea dif- 
fimilar in fize, length, and direflion ; the two lungs dif¬ 
fering in fize and in the number of their lobes, &c. The 
organs of exhalation and abforption, the ferous mem¬ 
branes, the thoracic dufil, and the right lymphatic trunk, 
as well as the other abforbing veflels, have every-where 
an irregular diftribution. Among the glands we fee the 
mucous follicles every-where fcattered irregularly. The 
pancreas and liver are out of all fymmetry: the kidneys 
differ in pofition, fize, &c. 
It is apparent from thefe confiderations, that the organs 
of the animal life in man are efl'entialiy charafilerifed by 
fymmetry; whije thofe of the internal life have the con- 
llant chara filer of irregularity in their external forms. It 
follows alfo from this view, that the animal life is in a 
manner double ; and its phenomena, executed at the fame 
time on the two tides, form an independent fyftem on 
each fide, of which one may'go on while the other ceafes. 
This happens in thofe cafes of paralyfis called hemiplegia, 
where the animal life is annihilated on one fide of the 
body', fo that the individual has no relation to furround¬ 
ing objects; while the prefervation of fenfation and mo¬ 
tion on the other fide give him all the ufual powers. The 
median line in thefe cafes accurately diftinguifhes the 
found from the affefiled fide. 
In the organic life, on the contrary, all the parts con- 
fpire to form one fyftem, fo that the funfilions of one fide 
cannot be interrupted without thofe of, the other being 
affefiled. The liver on the left influences the ftate of the 
ftomach on the right; if the colon ceafe to afil on one 
fide, that of the other cannot goon ; the fame caufe that 
ftiould arrell the circulation in the large venous trunks 
and theright fide of the heart, would flop it alfo in the 
left fide, and in the arteries, See. Hence, if all the or¬ 
gans of the internal life on one fide ftiould have their 
functions ftoppfid, thofe of the oppofite fide would necef- 
farily remain inafilive, and death muft follow. This af- 
fertion, however, is general, and applies to the organic 
funfilions collefilively; fome of the organs are in fafit 
double, and may fupply each other’s places, as the kidney 
and lung. 
Bichat proceeds to point out the differences by which 
the animal and organic lives are diltinguifhed when in a 
ftate of afition. He obferves that harmony is to the 
funfilions of the organs what fymmetry is to their con¬ 
formation ; it fuppofes a perfefil equality of force and 
afilion, as fymmetry indicates an exafil analogy between 
the external form and the internal ftrnfilure. It is a con- 
fequence of the law of fymmetry; for two parts, effen- 
tialiy alike in their Itrufilure, cannot afil differently. This 
realoning would lead to the general pofition, that harmony 
is the character of the external funfilions, and difcord-ance 
the attribute of the internal ones. He then enters at con- 
fiderable length into a detailed conlideration of this fub- 
jefil; but does not fucceed in proving the point. 
A more important diltinfitive charafterof the two lives 
is drawn from the periodical intermiflions of the external 
funfilions, and the uninterrupted continuity of the inter¬ 
nal ones. Whatever fufpends p"efpiration and circulation, 
fufpends and even annihilates life if it be continued. 
All the fecretions go on uninterruptedly ; if fome periods 
of remiffion are obferved, as in the bile and faliva, when 
digeftion and maftication are not going on, thefe affefit 
only the degree of afilivity, and not the entire exercife of 
the funfilion. Exhalation and abforption fucceed each 
other without ceafing; nutrition is never inafilive; the 
double motion, of compofition and decompofition, from 
which it refults, ends only with life. 
In this concatenation of the organic phenomena, each 
funfilion depends immediately on thofe which precede it. 
The circulation is the centre of the whole, and imme¬ 
diately connefiled with their exercife; if that is difturbed, 
the others Ianguifti; they ceafe if the blood no longer 
moves. Thus, the numerous wheels of a clock flop as 
fcon as the pendulum, which fets them all in motion, is 
at reft. Not only is the general afilion of the organic life 
connefiled to the particular afilion of the heart, but each 
funfilion is alfo feparately connefiled to all the others. 
Without fecretion there would be no digeftion; with¬ 
out exhalation no abforption ; without digeftion, no nu¬ 
trition. We may, therefore, lay down as a general cha- 
rafilerofthe organic funfilions, their continuity of afilion 
and mutual dependence on each other. 
On the contrary, confider each organ of the animal life 
in the exercife of its funfilions; you will fee conftantly 
alternations of afilivity and repole, complete intermiflions, 
and not remiflions like what may be feen in fome of the 
organic phenomena. Each fenfe, fatigued by a long con¬ 
tinuance of fenfations, becomes momentarily unfit for the 
reception of new ones. The ear is not excited by founds, 
and the eye is doled again!! the light, merely becaufe the 
refpefilive funfilions have been exerted for fome time. Fa¬ 
tigued by a long exercife of the perception, the imagina¬ 
tion, memory, Sec. the brain requires a iiifpenfion of afilion 
proportioned to the duration of the preceding afilivity, in 
order to recruit the powers, without which it could not 
again become afilive. 
"When a mufeie has been contrafiled ftrongly, and for a 
confiderable time, it cannot perform new contrafilion until 
after a certain,interval of relaxation. Hence there are 
intermiflions in the exertions of the locomotive and vocal 
powers. 
This intermifiion in the animal life may be either partial 
or general. The former is feen when a particular organ 
has been a long time in exercife, the others remaining 
inafilive; this organ then relaxes; it fleeps while the 
others are awake. Each animal funfilion, therefore, is 
not in an immediate dependence on the others, as is the 
cafe with the organic lunfilions. When the fenfes are 
doled again ft external objeds, the afilion of the brain may 
(till continue; memory, imagination, and reflefition, are 
then often exercifed. Locomotion and the voice may 
ftill remain : w'hen the latter are interrupted, the funfilions 
of the fenfes ftill go on. The animal can fatigue any 
part feparately. Each, therefore, fnould have the power 
of refting in order to recruit its forces feparately ; this 
is the partial lleep of the organs. General fleep is the 
aflemblage of thele particular afils, and arifes from the law 
which we have juft illullrated. 
Concerning the powers or properties which caufe life, or 
the funfilions, Bichat admits many kinds. The two 
fundamental ones, like every one elfe, he confiders to be 
fenlibility and contrafilility; but he foon fubdivides 
them, thereby admitting a greater number. He fays that 
the vital properties may be reduced to thofe of perceiving 
or feeling (lenfibility), and moving (contrafilility) : each 
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