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It may not therefore be unentertaining to this 
learned Society, who fo fludioufly promote every ufe- 
fui inquiry, not only to have a demonfirative proof 
of the exigence of lymphatics in a part of the human 
body where they have not as yet been difcovered ; ^ 
but alfo to have an opportunity of knowing that the 
true origin of thefe velTels may eafily be fhewn. 
As to their precife origin, it has indeed been con- 
jedured, and very reafonably, from experiments a 
pojieriori. 
It has been fiippofed they arife from all the furfaces 
and cavities of the body ; becaufe thin fluids and fubtle 
•particles will be taken up from fuch cavities, or fur- 
faces, and will be readily enough conveyed into the 
blood : but then it has never been fliewn, that they do 
arife from any one fuch furfacc or cavity. 
Commonly, the lymphatics are never filled from 
their beginnings, or little orifices. When they have 
been injedled, it has always been done by ufing fome 
violence; either by cutting into them, burfting, or 
tearing them afunder ; fo that the inje<flion rather 
frets in fome how at the fide, and not at the cxtrc- 
mity of the vefiTel. 
The ladteal vcfiels perhaps cannot, at leaft have 
never been, to my knowledge, injedled from the 
cavity of the intefiine in the dead. body. It is 
prefumed, that, as the lymphatics are fimilar to thefe 
in other refpects, their origins mufl: be alfo fimilar : 
that if the orifices of the ladteals are too fine to be 
difcovered, the mouths of the lymphatics are alfo too 
delicate to be traced out. But with regard* to the 
lymphatics of the human urinary bladder, it is cer- 
tainly otherwife. When the prart is frefli and found, 
2 we 
