100 
OF THE VESSELS 
than any other liquor with -which it can be compared. For 
the straining off this fluid from the digested aliment in the 
course of its long progress through the body, myriads of 
capillary tubes, i. e. pipes as small as hairs, open their ori¬ 
fices into the cavity of every part of the intestines. [PL 
XIX.] These tubes, which are so fine and slender as not 
to be visible unless when distended with chyle, soon unite 
into larger branches. The pipes, formed by this union, 
terminate in glands, from which other pipes of a still larger 
diameter arising, carry the chyle from all parts, into a 
common reservoir or receptacle. This receptacle is a 
bag large enough to hold about a table-spoon full; and from 
this vessel a duct or main pipe proceeds, climbing up the 
back part of the chest, and afterwards creeping along the 
gullet till it reach the neck. Here it meets the river: here 
it discharges itself into a large vein, which soon conveys 
the chyle, now flowing along with the old blood, to the 
heart. This whole route can be exhibited to the eye; 
nothing is left to be supplied by imagination or conjec¬ 
ture. Now, beside the subserviency of this whole structure, 
to a manifest and necessary purpose, we may remark two 
or three separate particulars in it, which show, not only the 
contrivance, but the perfection of it. We may remark, 
first, the length of the intestines, which, in the human sub¬ 
ject, is six times that of the body. Simply for a passage, 
these voluminous bowels, this prolixity of gut, seems in no¬ 
wise necessary; but, in order to allow time and space for 
the successive extraction of the chyle from the digested 
aliment, namely that the chyle which escapes the lacteals 
of one part of the guts, maybe taken up by those of some 
other part, the length of the canal is of evident use and 
conduciveness. Secondly, we must also remark their per¬ 
istaltic motion; which is made up of contractions, follow¬ 
ing one another like waves upon the surface of a fluid, and 
not unlike what we observe in the body of an earth-worm 
crawling along the ground; and which is effected by the 
joint action of longitudinal and of spiral, or rather perhaps 
of a great number of separate semicircular fibres. This 
curious action pushes forward the grosser part of the ali¬ 
ment, at the same time that the more subtile parts, which 
we call chyle, are, by a series of gentle compressions, 
squeezed into the narrow orifices of the lacteal vessels. 
Thirdly, it was necessary that these tubes,which we denom¬ 
inate lacteals, or their mouths at least, should be as nar¬ 
row as possible, in order to deny admission into the blood 
to any particle which is of size enough to make a lodge- 
