502 
tinuous with that of the duct. Such observa- 
tions seem to me in a great measure conclusive 
on this subject; and I am strengthened in this 
view b the fact, that the capsules of the 
Malpighian bodies of the kidney are now 
universally considered to be perfectly closed 
vesicles, whereas they are in reality the ex- 
ed wall of the duct, as I have lately 
shown by several kinds of proof.* But what- 
ever may be the real fact in the matter under 
“es an it is admitted by all that the epithelium 
is formed in enormous quantities, and is being 
continually thrown off; which is the circum- 
stance chiefly intended to be insisted on at 
resent. 
In the healthy bile also, in the urine, and in 
various other secretions Dr. Henle has met 
with particles of epithelium detached from the 
ery passages, and in different stages of 
Turning to those two great emunctories, the 
liver and kidneys, in the secretions of which 
no trace of the epithelium of the secreting part 
of the organs can be detected, we might be 
disposed, on a slight consideration, to conclude 
the evidence they furnish to be unfavourable to 
the general position here advanced. We must, 
indeed, be content for the present to acknow- 
ledge that it is less plain and direct, and 
shrouded in our great ignorance concerning the 
play of chemical affinities in living bodies; 
ut still it is too interesting and important to 
be passed over in silence. Though the epithe- 
lium of these organs be not detached entire, as 
in many other cases, there is much, in each 
instance, to explain the discrepancy consistently 
with the theory in question. 
I have described the lobules of the liver as 
consisting of a solid plexus of capillary blood- 
vessels, in the meshes of which is a congeries 
of epithelial particles. We possess no accurate 
account of the mode of termination of the 
biliary ducts; but it seems clear, from the 
small meshes of the vascular plexus being 
completely filled by the epithelium, that no 
true ducts, i. e. tubes, penetrate the substance 
of the lobules: the tubular ducts probably 
commence on the surface of the lobules. The 
epithelium of the lobules is doubtless conti- 
nuous with that of the ducts, but the cavity of 
the ducts and their basement membrane termi- 
nate at the surface of each lobule. Though the 
cavity of the ducts be not continued within the 
lobule, yet it is very possible that injection 
urged along the ducts might insinuate itself by 
the side of the epithelium into the interstices 
of the vascular plexus, and thus, like the 
epithelium itself, form a solid piceus within 
e lobule. This appearance probably led Mr. 
Kiernan to describe the termination of the ducts 
as forming a plexus within the lobule, the 
lobular biliary plexus. And this description 
must be allowed to be essentially correct; for 
although the cavity of the duct cease at the 
surface, the epithelium of the lobule is, in 
respect of function, its real continuation. I 
have further observed, that although the epithe- 
* Phil. Trans. 1842, Pt. I. p. 59. 
MUCOUS MEMBRANE. . 
-secretion, and to prevent the latter from 
lium of the lobule has, on the whole, a plexi>— 
form arrangement, yet its particles in some ‘ 
measure affect a radiating direction from the — 
central axis towards the circumference, a 
towards certain parts only; and when veneal 
is broken up by violence, the resulting frag- 
wont of opabenee are apt to consist of a 
inear series 0 icles. Many of the 4 
too, are eaten the erage ace aal 
appearance of having been recently formed and — 
as yet incompletely developed. It is ai 
remarkable that the particles should contain 
granules of oily matter in their interior; for 
although chemical analysis has detected di 
rences between this substance and cholesterine,* 
yet as the chief peculiar principles of the bile 
are forms of hydro-carbon, the coincidence — 
cannot be an accidental one. It is not con- 
tended that the contents of these particles are 
the finished secretion, but rather that their 
chemical constitution undergoes some modifi- 
cations during the disintegrating process. 
it is worthy of notice, that in many cases wher 
the decarbonizing function of the lungs is 
slowly but greatly interfered with, as in phthisis 
pulmonalis, and where the liver is consequently 
called into increased activity as a compensati ng 
organ, these oily globules exist in such abun. 
dance and size as to gorge and swell the parti 
cles (and therefore the whole viscus) to near 
double their natural bulk.+ But this is not al 
the evidence, that this epithelium is the souree 
of the bile. I am informed by my friend, Dr 
W. Budd, that Dr. Henle in his recent editio 
of Soemmering, of which I have not yet bee 
able to obtain a copy, describes the epithelic 
particles as appearing yellow or yellowi: 
in direct light, and as probably containing 
He also states that the presence of the fatt 
globules in the epithelium is inconstant, am 
corresponds with the varying fatty contents 6 
the bile. He is unable at present to determine 
in what manner the contents of the particles 
find their way into the ducts. 4q 
The foregoing facts, taken together, afford 
very strong presumption that the epithel 
particles of the lobules are the agent assimilatit 
the secretion from the blood. It would 
still more satisfactory if particles could be fe 
undergoing decay. Meanwhile it seems i 
possible to assign to them any other office 
it be granted that the sole function of 
is to secrete bile. For in the case of o 
glands, the only other use that can with 
degree of plausibility be attributed to the 
thelium is that of its serving to defend 
secreting membrane from the contact of 
a 
ss 
se 
entering the blood. And it cannot exist 
that purpose in the liver, because it is | 
the only structure besides the bloodvessels 
does not constitute a lining membrane. 
_The peculiarity in the minute structu 
the kidneys, which bears on the prese 
tion, is of a kind entirely different 
presented by the liver, and yet tends to 
a similar conclusion. It consists of a Sp 
* Kuehn, Kastner’s Archiv. xiii. p. 337, — 
+ Author in Lancet, Jan, 1842. da 
