BLOOD. 
ftippofed, that, in fucli cafes as that juft now mentioned, 
the veflels are not formed in the coaguhun, but come 
front the neighbouring arteries, it is equally an argument 
that the blood is alive; for the fubftance into which vel- 
fels ftioot nut ft be fo. The very idea, that fucli a quan¬ 
tity of dead matter as the whole ntafs of blood, circulat¬ 
ing in a living body, is a'bfolutely abfurd. 
Thole who have ventured to oppofe this dodlrine, and 
the evidence of Scripture with it, (Levit. xvii. 11,14. 
Deut.x ii. 23.) confider the brain and nervous fyfte 111 as 
the fountain of life ; and that, f'o far from receiving its 
life from the blood, the nervous fyftem is capable of in- 
ftantaheoufly changing the crafts of the blood, or any other 
animal fluid ; and, though the nervous fyftem cannot con¬ 
tinue its adtion for any length of time if the adtion of the 
blood-veflels is fufpended, yet the heart and blood-veflels 
cannot adt for a Tingle moment without the influence of 
the nervous fluid. For this reafon, fay they, it is plain 
\ve mu ft fuppofe the nervous fyftem, and not the blood, 
to contain properly the life of the animal, and confequently 
to be the principal vital organ. The fecretion of the vi¬ 
tal fluid from, the blood by mean's of the brain, is, by 
the fupporters of this hypothefis, denied. They fay, 
that any fluid fecreted from the blood nnift be aqueous, 
inelaftic, and inadlive ; whereas the nervous fluid is full 
of vigour, elaftic, and volatile, in the higheft degree. 
The great neceftity for the circulation of the blood through 
all parts of the body, notvvithftanding the prefence of the 
nervous fluid in the fame parts, they fay is, becaufe forne 
degree of tenfton is neceflary to be given to the fibres, in 
order to fit them for the influx of the nervous fluid; 
and this tenfion they receive from the repletion of the 
blood-veflels, which are every where difperfed along with 
the nerves. 
To follow this opinion through every argument, would 
prove tedious and unneceflary, as the following fliort ob- 
l’ervation will decide the matter abfolutely againft the pa¬ 
trons of the nervous fyftem. In the firft place, if we can 
prove the life of the human body to have been commu¬ 
nicated from a fluid to the nervous fyftem, then the ana¬ 
logical argument will be very ftrongly in favour of the fup- 
pofition that the cafe is fo ftill. Now, that the cafe once 
was fo, is mod evident ; for the human body, as well as 
file body of every other living creature, in its firft: (late, 
is well known to be a gelatinous mafs, without mufcles, 
nerves, or blood-velfels. Neverthelefs, this gelatinous 
matter, even at that time, contained the nervous fluid. 
Of this there can be no doubt, becaufe the nerves are 
formed out of it, and have their power originally from it; 
and what is remarkable, the brain is obferved to be that 
part of the animal which- is firft formed. Of this gela¬ 
tinous fluid we can give no other account, than that it is 
the nutritious matter from which the whole body appears 
to be formed. At the original formation of man, and 
other animals, therefore, the nutritious matter was the 
fubftratitm of the whole body, confiding of mufcles, 
nerves, blood-veflels, &c. nay more, it was the immedi¬ 
ate efficient caufe of the nervous power itfelf. Why 
lhould it not be fo now as well as then ? Again, in the 
formation of the embryo, we fee a vital principle exifting 
as it were at large, and forming to itfelf a kind of regu¬ 
lator to its own motions, or a habitation in which it 
choofes to refide, rather than to ac'l at random in the fluid. 
This habitation, or regulator, was undoubtedly the ner¬ 
vous fyftem, and continues fo to this moment; but at the 
fame time, it is no lefs evident that a nutritious fluid was 
the immediate origin of thefe fame nerves, and of that 
very nervous fluid. Now we know, that the fluid which 
in the womb nourifties the bodies of all embryo animals, 
is neceflarily equivalent to the blood which nourifties the 
bodies of adult ones ; and confequently, as foon as the 
blood became the only nutritious juice of the body, at 
that fame time the vital or nervous fluid took up its refi- 
dence there, and from the blood diffufed itfelf along the 
nerves, where it was regulated exactly according to the 
127 
model originally formed in the embryo. Perhaps it may 
be laid, that the vital power, when once it hath taken 
polfeflion of the human or any other body, requires 
no addition or fupply, but continues there in the fame 
quantity from firft to lalt. If we fuppofe the nervous- 
power to be immaterial, this will indeed be the cafe, and 
there is an end of reafoning upon the fubjedl ; but, if we 
call this power a volatile and elaftic fluid, it is plain that 
there will be more occafion for recruits to fucli a power 
than to any other fluid of the body, as its volatility and 
claft.city will promote its efcape in great quantities through 
every part of the body. It may perhaps be objected, that 
it is abfurd to fuppofe any fluid or mechanical caufe, ca¬ 
pable of putting matter in fucli a form as to direCt its own 
motions in a particular way : but even of this we have a 
pofitive proof in the cafe of the eledtric fluid. For if any 
quantity of this matter has a tendency to go from one place 
to another where it meets with difficulty, thro’ the air for 
inftance, it will throw filial 1 conducting fubftances before 
it, in order to facilitate its progrefs. Alfo, if a number of 
fin all and light conducting fubftances are laid between two 
metallic bodies, fo as to form a circle, for example ; a 
fliock of eledtrity will deftroy that circle, and place the 
fmall conducting fubftances nearer to a ftraight line be¬ 
tween the two metals, as if the fluid knew there was a 
fliorter paffage, and refolved to take that, if it fhould have 
occafion to return. N Laftly, it is univerfally allowed, that 
the brain is a decretory organ, made up of an infinite num¬ 
ber of fmall glands, which have no other excretories than 
the medullary fibres and nerves. As a confiaerable quan¬ 
tity of blood is carried to the brain, and the minute arte¬ 
ries end in thefe fmall glands, it follows, that the nervous 
fluid mujt come from the blood. Now-, there is no gland what¬ 
ever, in the human or any other body, but will difeharge 
the fluid it is appointed to fecrete, in very confiderable 
quantity, if its excretory is cut. Upon the cutting of a 
nerve, therefore, the fluid fecreted by the brain ought to 
be difeharged ; but no fucli difeharge is vifible. A Anall 
quantity of glairy matter is indeed difeharged from the 
large nerves; but this can be no other than the nutritious 
juice neceflary for their fupport. This makes it plain, 
even to demonftration, that tiie fluid fecreted in the brain 
is invifible in its nature ; and, as we know the nervous fluid 
hath its refidence in the brain, it is very probable, lo ufe 
no ftronger expreflion, that.it is the peculiar province of 
the brain to fecrete this fluid from the blood, and confe¬ 
quently that the blood originally contains the vital princi¬ 
ple. In confirmation of this hypothelis, fee the article 
Conception. See alfo Hunter’s Treatife on the Blood, 
by Everard Home, 1794; Hewfon on the Properties of 
the Blood ; Berdoe on the Circulation ; Fordyce’s Ele¬ 
ments, and Haller’s Phyfiology. 
Blood was formerly held in great efleem as a medicine 
for fome particular difeafes. Baths of the blood of infants 
have been recommended as an infallible remedy for the ele- 
phantiafis, &c. and the blood of goats and fome other ani¬ 
mals was ufed by the Galenifts, and is recommended even 
by Dr. Mead in pleuriftes : but the firft abominable me¬ 
dicine, as well as the other, is now del'ervedly exploded- 
The principal ufe of blood in the arts is for making Pruf- 
fian blue, or fometintes for clarifying certain liquors ; it 
is alfo recommended in agriculture as an excellent manure 
for fruit-trees. A mixture of blood with lime makes an 
exceedingly ftrong cement.; and hence it is of ufe in the 
preparation of fome chemical lutes, in making floors, See. 
As a food, it hath been difputed whether blood really af¬ 
fords any nourifhment or not. The beft judges now, how¬ 
ever, are generally agreed that it is very nutritious ; and 
though out of the body, like the white of an egg, it is very 
infoluble, yet, like that too, in the body it is commonly 
of eafy digeftion. It is, however, highly alcalelcent in 
hot climates; on which account the prohibition of it to 
the Ifraelites was very proper. Even in this country, 
w hen blood was ufed as food in great quantity, the (curvy 
was more frequent than at other times; but, to a moderate 
