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I N O C U L 
fefled with any contagious fever. 3. Whgn they are af- 
fe&ed, at the time of inoculation, with foine chronic cu¬ 
taneous diforders. 
“ i. The qualities of the vaccine fluid are altered foon 
after the appearance of an inflamed areola round the vefi- 
cte; and the fluid, although,taken out of a veficle in the 
belt poflible ftate, may be injured by heat, expofure to 
air, moifture, ruft, and other caufes. When fcabs are 
formed over variolous puftules and vaccine veficles, the 
matte'r they afford is often acrid and putrefcent, and, if 
inoculated, it perhaps neither communicates the vaccine- 
pock nor the frnall-pox, but produces, a fatal dileafe, with 
fymptoms fimilar to thofe which arife from flight wounds 
received in diffefling putrid bodies. Should the puftules 
of fmall-pox remain entire till the twentieth day of erup¬ 
tion, matter taken from them, even at that period, will 
fometimes communicate, by inoculation, the difeafe in its 
ufual form, though perhaps with confiderable virulence. 
We are, however, now affured on good authority, that 
matter improperly kept, or the thick matter taken from 
collapfed and fcabbing variolous puftules, and ufed for 
the purpofe of inoculation, does not always produce the 
fmall-pox, nor prevent the future occurrence of that dif- 
e*fe, although the perfons inoculated may have had in¬ 
flammation and fuppuration of the arm, and pains in the 
axilla, with fever and eruptions on the ninth or tenth day. 
In like manner, if the vaccine fluid employed be taken at 
a late period, as from the twelfth to the eighteenth day, 
it does not always produce the genuine cellular veficle, 
but is in fome cafes wholly inefficient, while in others it 
fuddenly excites a puftule, or ulceration, in others an ir¬ 
regular veficle, and in others eryfipelas. Similar appear¬ 
ances are obferved, when fluid taken from a perfect vefi¬ 
cle on the fixth, feventh, or eighth, day, has been injured, 
before its application, by fome of the caufc-s above enu¬ 
merated. In addition to them, I may obferve that if the 
veficle .be ruptured, at an early period, by friflion or 
ficratching, the inoculation fometimes proves imperfeft. 
Failures may have alfo been occafioned by repeatedly 
puncturing or draining the veficle on two or three fuc- 
ceflive days. The fluid, which is afterwards fecreted into 
the cells thus exhaufted, may, by a difference of proper¬ 
ties, or by too much dilution, be rendered incapable of 
afting fully, either on the perfon from whom it is taken 
or on thofe to whom k is communicated. Some of the 
early failures in perfons inoculated at different public in- 
ftitutions are perhaps referable to this caufe, the demands 
for vaccine fluid in 1799 and 1800 having been very nu¬ 
merous, the cafes to fupply them comparatively few. 
“ z. Eruptive fevers, and other febrile difeafes, interfere 
•with the progrefs of the vaccine veficle. The mealies, 
fcarlatina, varicella, typhus, and influenza, appearing foon 
after vaccination, either render it ineffective, or fufpend 
the action of the virus, fo that in fome cafes, the progrefs 
of the veficle is very (low, and the areola is not formed 
till the fourteenth day or later, and fometimes not at all. 
Dr. Jenner has recorded the cafe of a child, on whom the 
fcarlatina, witty a fore-throat, appeared on the ninth day 
of vaccine inoculation. The veficle enlarged as ufual, 
yet there was a total fufpenfion of the areola, until the 
fcarlatina had retired from the conftitution. In a lifter 
of this patient, the fever and fcarlet efflorefcence took 
place faintly on the fame day, but fuddenly difappeared, 
the areola having been formed round the veficle. Four 
days afterwards, on the decline of the veficle, the fcarla¬ 
tina anginofa returned with its ufual fymptoms. 
“3. The cutaneous difeafes which fometimes impede 
the formation of the genuine vaccineve ficle, are herpes, 
(including the fhingles and veficular ringworm,) the dry 
and humid tetter, and the lichen, but efpecially the por- 
rio-o (or tinea), comprifing the varieties denominated crufta 
laCtea, area, achores, and favi, all of which are conta¬ 
gious. To thefe perhaps fhould be added the itch and pru¬ 
rigo. 
“Imperfeft: vaccination is not characterized by any uni- 
A T I O N. 
form fign or criterion, but exhibits, in different cafes, very 
different appearances, as puftules, ulcerations, or veficles 
of an irregular form. The vaccine puftule is conoidal j 
it increafes rapidly from the fecond to' the fifth or fixth 
day, being railed on a hard inflamed bafe, with diffufe 
rednefs extending beyond it on the fkin. It is ufually 
broken before the end of the fixth day, and is foon after 
fncceeded by an irregular yellowifh brown fcab. The 
rednefs difappears within a day or two, and the tumour 
gradually fubfides. According to Dr. Jenner, its com¬ 
mencement is marked by a troublefome itching, and it 
throws out a premature efflorefcence, fometimes extenfive, 
but feldom circumfcribed, or of fo vivid a tint as that 
which furrounds the veficle completely organized ; and 
(which is more charaCteriftic of its degeneracy than the 
other fymptoms) it appears more like a common fettering 
produced by a tborn, or any other fmall extraneous body, 
flicking in the fkin, than a veficle excited by the vaccine 
virus. It is generally of a draw colour, and when punc 
tured, inftead of the colourlefs tranfparent fluid of the per¬ 
fect veficle, its contents are found to be opaque.” 
The chief nicety and difficulty of vaccination confifts 
in diftinguifliing the irregular veficles; and we fhall here 
apply to the fame fource. “ I have obferved three forts- 
of thefe irregular veficles. The firft is a fingle pearl- 
coloured veficle, fet on a hard dark-red bafe, flightly ele¬ 
vated. It is larger and more globate than the puftule 
above reprefented, but much lefs than the genuine vefi¬ 
cle ; its top is flattened, or fometimes a little deprelfed, 
but the margin is not rounded or prominent. The fe¬ 
cond appears to be cellular like the genuine veficle, but 
it is fomewhat fmaller, and more feflile, and has a iharp 
angulated edge. In the firft the areola is ufually diffufe, 
and of a dark rofe-colour; in the fecond it is fometimes 
of a dilute fcarlet-colour, radiated, and very extenfive, as 
from the fling of a wafp. The areola appears round thefe 
veficles on the feventh or eighth day after inoculation,, 
and continues more or lefs vivid for three days, during 
which time the fcab is completely formed. The fcab is 
fmaller and lefs regular than that which fucceeds the ge¬ 
nuine veficle; it alfo falls off much fooner, and, when le- 
parated, leaves a fmaller cicatrix, which is fometimes an¬ 
gulated. The third irregular appearance is a veficle with¬ 
out an areola. 
“The vaccine puftule, and ulceration, may fometimes 
arife from the infertion of effete or altered virus ; but they 
moftly occur in perfons labouring under the eruptive com¬ 
plaints formerly mentioned. 
“The irregular veficles are produced by fome of the 
caufes already enumerated. The veficle without an areola 
takes place if the perfon inoculated have previoufly re¬ 
ceived the infeftion of the fmall-pox, or if he be aftefted 
with fome other contagious fever, during the progrefs of 
vaccination.” Thefe irregular veficles are fometimes a fe- 
curity from fmall-pox, and the matter which they pro¬ 
duce will occafionally excite a genuine veficle, but they 
fhould in no inftance be depended on. 
It was for a time fuppofed that vaccina (cow-pox), and 
variola (fmall-pox) were fimilar difeafes, but that from 
accidental circumftances the former was milder. It was 
cutting the knot rather than explaining the fource of the 
fufceptibility being deftroyed ; but the very exiftence of 
this f ufceptibility, not called into a&ion for four thoufand 
years, is a problem of much greater difficulty. It was 
found, however, on examination, that, when each difeafe 
was introduced at the fame time, the one did not check 
the other; both proceeded in their own way, but the vac¬ 
cina modified a little the appearance of variola; and it 
feems, from Dr. Willan, that it modified the puftule in 
the manner which variolous eruptions, after vaccination, 
fometimes aflume. Fig. 6, on the annexed Plate, exhi¬ 
bits a vaccine veficle on the ninth day, as it appeared on 
the arm of a boy who had been inoculated with variolous 
matter ten days before vaccination. B is a variolous puf¬ 
tule at a little aiftance from the veficle ; C another va¬ 
riolous 
