:S4 INJECTION. 
its own weight is fufficient; but the operator muft recol¬ 
lect, that the momentum is in proportion to the perpen¬ 
dicular height of the column, not its diameter. Quick- 
filver is chiefly ufed in injecting the lafteals and lympha¬ 
tics, the veflels of the parotid glands, of the teftis, and of 
the mammas; fometimesthe arteries and veins of the hand. 
In general, the younger the animal is, the injection 
will go farther; and the fame will happen when the fluids 
have been exhaufted by difeafe. In the firft cafe, the 
fmall veflels are larger; in the fecond, they are more 
empty. The lefs folid the part is, more veflels will be 
filled ; and, the more membranous, the brighter and 
more beautiful the preparation will appear. The great 
objeft in injeftions, therefore, is, to empty the veflels, to 
relax the folids, and prevent the too rapid coagulation of 
the injeCted fluids. Water is, therefore, firfl injected, 
till it returns colourlefs by the veins; the water is pro¬ 
pelled by injeCting air, and the air is afterwards fqueezed 
out. But the water cannot be wholly feparated, and the 
particles of this fluid interpofed between thofe of the in¬ 
jection occafion its breaking. It is therefore more com¬ 
mon to truft to maceration for fome time in the water, 
and fqueezing the veflels, fo as to evacuate the fluids by 
the divided end. 
When the fyringe, injections, and fubjeft, are all in 
readinefs, one of the fecond fort of pipes is chofen, as near 
to the diameter of the veflel by which the injection is to 
be thrown as poflible: for, if the pipe be too large, it is 
almoft needlefs to fay it cannot be introduced. If the 
pipe be much fmaller than the veflel, it is fcarcely poflible 
to tie them fo firmly together, but, by the wrinkling of the 
coats of the veflel, fome fmall paffage will be left, by 
which part of the injection will fpring back on the injec¬ 
tor in the time of the operation, andtheneareft veflels re¬ 
main afterwards undiftended by the lofs of the quantity 
that oozes out. Having chofen a fit pipe, it is introduced 
at the cut orifice of the veflel, or at an incifion made in 
the fide of it; and then a waxed thread being brought 
round the veflel, as near to its coats as poflible, by the 
help of a needle or a flexible eyed probe, tne furgeon’s 
knot is made with the thread, and it is drawn as firmly 
as the thread can allow ; taking care that it {hall be funk 
into the circular notch of the pipe all round, otherwife it 
will very eafily Aide off - , and the pipe will be brought out 
probably in the time of the operation, which ruins it. If 
there have been large veflels cut, which communicate with 
the veflels you defign to injeft, or if there are any others 
proceeding from the fame trunk, which you do not re- 
folve to fill, let them be all carefully now tied up, to fave 
the injefted liquor, and make the operation fucceed bet¬ 
ter in the view you then have. 
All this being done, both forts of injeftions are to be 
warmed over a lamp, taking care to ltir them conftantly, 
left thp colouring-powder fall to the bottom and burn. 
The oil of turpentine needs be made no warmer than will 
allow the finger to remain in it, if the fubjeft has been 
previoufly well warmed in water; when the maceration 
has not been made, the oil ought to be lcalding hot,'that 
it may warm all the parts which are defigned to be in¬ 
jected. The coarfe injeftion ought to be brought near to 
boiling. In the mean time, having wrapt feveral folds 
of linen round the parts of the fyringe which the opera¬ 
tor is to gripe, and fecured the linen with thread, the ly- 
ringe is to be made very hot by fucking boiling-water le- 
veral times up, and the pipe within the veflel is to be 
warmed by applying a fponge dipped in boiling water 
to it. 
After all is ready, the fyringe being cleared of the wa¬ 
ter, the injeftor fills it with the finer injeftion ; and then, 
introducing the pipe of the fyringe into that in the vef- 
lel, he prelfes them together, and either with one hand 
holds this laft pipe firm, with the other gripes the fyringe, 
and with his breaft pulhes the fucker; or, giving the pipe 
in the veflel to be held by an afliftant, in any of the ways 
mentioned in the defoription of thefe forts of pipes, lie 
gripes the fyringe with one hand, and puflies the fucke? 
with the other, and confequently throws in the injeftion,- 
which ought to be done flowly, and with no great force 
but proportioned to the length and bulk of the part to be 
injected and ftrength of the veflels. The quantity of this 
fine injeftion to be thrown in is much to be learned by 
ufe. “ The only rule I could ever fix to myfelf in this 
matter,” fays Dr. Monro, (Effays, vol. i.) “ was to continue 
pufliing till I was fenfible of a ftop which would require 
a confiderable force to overcome. But this will not hold 
where all the branches of any veflel are not injefted ; as 
for inftance, when the veflels of the thorax only are to be 
injefted ; for the aorta bears too great a proportion to the 
branches fent from it, and therefore lefs fine injeftion is 
requifite here. As foon as that ftop is felt, the fucker of 
the fyringe is to be drawn back, that the neareft large 
veflels may be emptied.” Then the fyringe is taken off, 
emptied of the fine injeftion, and filled with the coarfer, 
which is to be pufiied into the veflels quickly and forci¬ 
bly, having always regard to the ftrength and firmnefs of 
the veflels, bulk, Sec. of the part. Continue to thruft the 
fucker, till a full ftop, or a fort of pufli backwards, is 
felt, when you muft beware of thrufting any more, other- 
wife fome of the veflels will be burfted, and the whole, 
or a confiderable ftiare, of the preparation you deffoned* 
will be fpoiled by the extravafation; but rather immedi¬ 
ately flop the pipe by the turn-cock, and take out the fy¬ 
ringe to clean it, and allow fufficient time for the coarfe 
injeftion to coagulate fully, before any part is diffefted. 
Ruyfch, immediately after throwing in the injeftion, put 
the body into cold 'water, and ftirred it continually for 
fome time, to prevent the vermilion feparating from the 
tallow. 
A foetus may be injefted by the umbilicus; a child or 
an adult, by the aorta afeendens from the left ventricle. 
Injeftion by the aorta fills only the arteries ; but by the 
umbilicus of a foetus both arteries and veins are injefted. 
Thus far of the fanguiferous fyflem. The injeftion of 
the lymphatic fyjlem is much more difficult, on account of 
the extreme fmalinefs of the veflels; fo that till very late¬ 
ly it was confidered as imprafticable. Methods indeed - 
had been attempted for this purpofe-; but, by reafon of 
the improper form of the inftruments, and the inferior 
fkill of anatomifts in former times, we may juftly look 
upon this as one of the mod modern improvements in 
anatomy. 
The firfl thing to be confidered, when the lymphatics 
are to be injefted, is a proper method of difeovering them 
for this is by no means an eafy matter, on account of 
their fmalinefs and tranfparency. To find out thefe vef- 
fels, the fubjeft muft be viewed in a proper place, where 
the light is neither very ftrong nor very weak. Mr. Shel¬ 
don, who has written a treatife upon this fubjeft, recom¬ 
mends a winter forenoon from ten to two; it being chief¬ 
ly in the winter feafon that anatomical preparations are 
made, and becaufe at that time of the day the lio-ht is 
more clear and fteadv. He fays alfo, from his own expe¬ 
rience, that the light paffmg through the glafs of a win¬ 
dow is better for this purpofe than the open air, as the 
veflels are more diftinftly feen. The injefting of thevef- 
fels is likewife rendered more difficult in rhe open air by 
the eale with which the humidity is evaporated from 
them. It will likewife be neceffary to incline the part in 
various ways to the light, as fome of the veflels are moil 
eafily difcoverable in one pofition and fome in another. 
The lafteal trunks under the peritoneal coats of the in- 
teftines, and the lymphatics on the external furfaee of the 
liver. See. particularly require this method. He dif'eom- 
mends the ufe of magnifying glafles. “I am perfuaded 
(fays he) that thofi:, who attempt to find them through 
this medium, will not acquire that vifus eruditm which is 
obtained to a l'urprifing degree by thofe who have been 
much experienced in injecting lymphatic veflels. A la¬ 
teral light is likewife preferable to an horizontal, even 
to an oblique, (ky-iight. 
The 
