31 
PATHOLOGY. 
•experiment. The art of injecting the veffels of the dead 
body, which has been difcovered and carried to great 
perfection fince his time, has Shown a continuation of 
canal joining the two fyftems of blood-veffels ; and the 
employment of the microfcope has completed the proof, 
by demonstrating the circulation in the tranfparent parts 
o ffrogs, See. during life. The transfufion of the blood 
o fone animal into the veifels of another, which has been 
performed with fuccefs in many inftances, has added 
another ftrong proof to the demonftration of the circu* 
iation. See the Hiftoire de l’Anatomie et de la Chi- 
rurgie of Portal, and the Bibliotheca Anatomica of Haller, 
in the articles concerning the writers whofe names are 
mentioned in this account. 
Francis de le Boe, otherwife Sylvius, was born at 
Hanau in 1614 ; and became profeflor of medicine at the 
univerfity of Leyden in 1658. He will be therefore 
readily distinguished from James du Bois, who is alfo 
called Sylvius, the mailer and violent adverfary of 
Vefalius, of whom we have fufficiently fpoken in the 
preceding Sedition. Francis Sylvius wasamuch morediltin- 
guiilied perfonage : he was alfo one of the earlieft advo¬ 
cates for Harvey’s doctrine of the circulation of the 
blood, and was the principal caufe of its reception into 
the medical ichool of Leyden. In other refpe'dts, how¬ 
ever, he was inilrumental in retarding the progrefs of 
medical fcience, by the invention of an hypothecs re- 
fpeCling the caufe of difeafes, which contributed much 
to excite the attention of the medical world, and to ex¬ 
tend his own fame. He aferibed all the morbid a< 5 tions 
of the vital fyftem to certain chemical operations, to 
fermentations, and ebullitions, which he believed gave 
origin to an excefs of acid or of alkali, to the neutraliza¬ 
tion of which all the efforts of the medical art were of 
courfe to be directed : whence he adminiltered volatile 
alkali, abforbent earths, and cordials, largely, paying 
little regard to the different llages of a diiorder, or the 
charafterof prevailing epidemics. The extent to which 
this doctrine was received and defended in molt parts of 
Europe, founded as it was upon a gratuitous hypothefis, 
and therefore produftive in many cafes of much mifehief, 
is furprifing, and the interruption which it occafioned to 
the improvement of medicine was confiderable. In faft, 
the chemical fyftem of Sylvius was admitted in almoll every 
country in which chemical fcience was cultivated : it 
was in Holland and in Germany however that it was 
carried to the moll extravagant pitch. While one phy- 
fician was earneftly employed in changing the acid Hate 
of the blood, another took great pains to counteract the 
alkaline properties of'the fame fluid. While Bontekoe, 
deducing all morbid phenomena from the vifeidity of 
fluids, eulogized the medical properties of tea, and 
drenched his patients with fifty cups in fucceflion of that 
liquor ; Van Ruftingh preferibed afliduoully large quan¬ 
tities of volatilefalts in the moll inflammatory complaints ; 
believing that the two elements of fire and water compofed 
the fubltance of all living bodies, and that to rellore 
their balance of power or equilibrium was the only pro- 
pofitum of the medical art. 
In our own country the more moderate of thefe tenets, 
with fome degree of modification, acquired celebrity. 
Willis, Flower, and others, adopted them, and, multi¬ 
plying on the acid and alkaline humours of Sylvius, af- 
ferted the exiftence of a great many different humours, 
viz, mucilaginous, vitriolic, corroiive, See. each of which 
they thought had the effeCt of producing a diforder J'ui 
generis: and hence they endeavoured to trace the various 
characters of difeafe. The phenomena of fever they like- 
wife attempted to explain according to the chemical laws 
of fermentation and ebullition. And, though Willis 
probably ufed thefe terms merely in an analogical fenfe, 
yet many phyficians of his time applied them to the 
human frame in their llriCl and chemical fignification. 
With refpeCt to the precife mode by which thefe aCiions 
were thought to bring about the phenomena of health or 
difeafe, the following is a brief fummary. Digellion was 
fuppofed to be carried on by fermentation. If this procefs 
was too aCtive, or, on the contrary, too weak, improper 
or tinfermented particles of aliment remained, which, 
when aflimilated and introduced into the blood, pro¬ 
duced the fame efteCt on that fluid as certain fubftances 
called ferments do upon vinous liquors; viz. they pro¬ 
duced fermentation. Now, viewing the matter in this 
light, thefe chemical pathologifts defined fever to be a 
fermentative procefs which nature instituted. for the pur- 
pofe of throwing off the aforefaid offending humours or 
cacochymias. If nature fucceeded in performing this 
talk, health was reflored ; if not, death enfued. Some 
difeafes were however produced by external caufes; for 
instance, infectious and contagious diftempers, &c. but 
then each of thofe diforders was brought about by means 
of humours, whether derived from the air by means of 
refpiration, or from aCtual contaCt. 
It is rather remarkable, that thefe phyficians admitted 
a third caufe of production of cacochymite, which went 
to overturn their whole fyltem. They exprefsly Hated, 
that organic difeafe of any of the vifeera engendered a 
peccant humour ; hence we naturally infer, that in this 
cafe the folid or fibrous (IruClure was the firft caufe of 
difeafe. 
In Italy, where mechanical fcience had made much 
progrefs, the chemical doCtrine obtained few fupporters. 
Indeed, anterior to the period we are treating of, Sanc- 
torius had, in his expofition of the cutaneous functions, 
taught phyfiologifts the illuilration which the vital de¬ 
rived from the confideration of the mechanical laws. He 
endeavoured to diltinguilh the different alimentary mat¬ 
ters according to their fpecific gravity, and referred 
difeafe to an obflruCled Hate of the exhalant fyftem: an 
opinion, however, which this author carried too far, and 
which was by no means conducive to his fuccefsful prac¬ 
tice. Neverthelefs it has been of great importance to his 
more enlightened fucceffors. 
Sydenham was born about the year 1624. One of the 
greateft benefits which he conferred upon the fcience of 
medicine was that of detaching phyficians from this and 
other hypothetical fyftems, and of leading them to the 
only true path, obfervation and experience. He intro¬ 
duced a great reform into medical pradice. Though not 
entirely free from the humoral hypothefes which were 
fo prevalent in his time, yet he took care to lludy na¬ 
ture with exa&nefs, and he reported her appearances 
with fidelity, even when oppofed to his own reafonings. 
Indeed in many parts of his writings he takes occafion 
to deprecate the practice of his predeceffors, becaufe they 
not only did not fufficiently remark the minute pheno¬ 
mena of difeafe, but becaufe they actually mifreprefented 
thofe phenomena for the purpofe of corroborating their 
fanciful theories. Nor did Sydenham admit the chemi¬ 
cal explanation of difeafe which was fo ilrongly infilled 
on by his contemporaries, and even fucceflors; for he 
exprefsly ftates, that, although he has no objection to the 
terms ebullition and fermentation, yet he rather ufes them 
as illustrating certain morbid proceffes by analogy than 
in their own commonly-received fenfe : and indeed he 
quotes fome very judicious arguments tending to dis¬ 
prove the identity of thofe chemical procefies with dif- 
eafed actions. This author followed very clofely the Heps 
of Hippocrates : like him, he was principally intent on 
obfervingthe minute features of difeafe, and of referring 
them to their obvious and immediate caufes; like hint, 
he admitted to a great extent the falutary operation of 
nature, and the deleterious agency of humours ; and 
like him too he paid particular attention to atmofphe- 
rical changes, and the effects of them on the human 
body. Indeed the chief merit of Sydenham confifted in 
writing clearly, fully, and from his own individual ob¬ 
fervation, the hiftory of difeafes. He inveftigated the 
minuteft changes which occurredin them, whether fpon- 
taneoufly or from the adtion of remedies, as well as thofe 
1 arifing 
