MUCOUS MEMBRANE. 
festly the same structures, detached and matted 
together. The secretion found in the tubules 
of the testis is chiefly composed of epithelial 
particles resembling those attached to the base- 
ment membrane of the tubules. Some of these 
are very perfect, others have undergone changes. 
It has been already stated that the seminal ani- 
malcules are most probably a developement of 
some of these particles, not altogether different 
in its nature from that of the cilia found upon 
them in other situations. The secretion of an 
ordinary mucous follicle is likewise made up 
of epithelial particles resembling those still 
attached to the membrane. The thick, semi- 
fluid mucus found in the stomach has been 
shown by Wasmann* to consist of rounded 
nucleated particles, which both in size and 
shape correspond with those of the stomach 
tubules. This mucus may be even seen pro- 
jecting from the cells into which these tubules 
discharge themselves, and no doubt can exist 
that the proper secretion of this organ is chiefly 
composed of the bulky epithelium thrown off 
by the tubules; a view corroborated by the 
fact,t that this mucous membrane, consisting 
almost solely of epithelium, when mixed with 
certain acids naturally existing in the gastric 
juice, evinces the same powers of dissolving 
alimentary substances as that wonderful men- 
struum itself. The same thing may be ob- 
served in the intestinal canal, where the adhe- 
_ Sive mucus is little else than the aggregated 
epithelial caps of the villi, together with that 
which has escaped from the vertical tubes of 
the membrane. These facts may be always 
verified in a healthy animal just killed, and 
may thus be shewn to be independent of any 
morbid action. The legitimate conclusion from 
them seems to be this: that the peculiar prin- 
ciples of these respective secretions are lodged 
in the epithelial particles ; having been depo- 
sited there from the blood, in the natural 
course of developement. In other words, the 
process of secretion in these cases consists in 
an assimilation of the material from the blood 
by an organized tissue, which, when fully de- 
veloped, is loosened and shed. 
This view, so captivating by its simplicity, 
has certainly much satisfactory evidence in its 
favour, and it may, at least, be regarded as 
‘sufficiently established to constitute a strong 
presumption in favour of the general position, 
that all secretion is primarily assimilation. 
That the epithelial particles, when their 
growth is completed, should detach themselves 
m a more or less entire state, in all cases, from 
the membrane to which they have adhered, 
cannot be supposed essential to this general 
position, and even the total absence of any 
vestiges of these particles from any particular 
secretion would scarcely form a valid argument 
against it. For at present we know of no reason 
_ why the assimilated material should not be 
_ gradually given up by a slow disintegration or 
p deliquescence of the particles, or even by a 
" - 
5 * De digestione nonnulla. Berol. 1839. 
_.t Miiller’s Archiv. 1836, page 90. Schwann, 
‘ uber das Wesen des Verdauungs prozesses. 
Pe 
501 
continual separation of it without a concomitant 
destruction of the particles themselves. 
But in numerous instances besides those that 
have been mentioned, there is more or less 
direct evidence of an actual shedding and con- 
tinual renovation of the epithelium. The scaly 
variety of this tissue, whether on skin or mu- 
cous membranes, is a wide-spread example of 
this: the particles may be observed to augment 
in size by the intus-susception of new material 
from the blood, afterwards to undergo a slow 
loss of substance, and, finally, to lose their 
connection with the body altogether. They 
retain their position till nothing but the nucleus 
and cell-membrane remain, till they are re- 
duced, as it were, to a mere skeleton. How 
the material thus separated from the body is to 
be distinguished from a secretion, it would not 
be easy to decide. In the saliva of the mouth, 
are present, not only detached scales, but globy- 
lar nucleated particles, of a very delicate aspect 
and regular character, which seem manifestly 
to come from the salivary glands. They differ 
in some respects from the epithelium of these 
organs, but appear most probably to be par- 
ticles of it altered by endosmose of the water 
of the secretion through the cell-membrane ; 
for the ultimate vesicles and ducts of these 
glands are not merely lined, but filled, with 
epithelial particles, which, being thrown off 
from the basement membrane, must in due 
time escape to make room for the advancing 
series: and yet none of them in an unaltered 
state are found in the saliva. 
I may in this place refer to an opinion 
recently entertained in Germany, that the 
secreting membrane of certain glands is arranged 
in the form of closed vesicles filled with nu- 
cleated particles, which, from time to time, 
are discharged, as the secretion, by the bursting 
of the cell in which they are contained. Henle* 
conceives that this arrangement exists in the 
mammary, salivary, and lachrymal glands, as 
well as in almost every mucous membrane, 
however apparently plain and simple. Was- 
mann + has described a similar structure in the 
middle part of the stomach of the pig. This 
view of the existence of closed vesicles is 
obviously at variance with the general view 
hefore given of the universal continuity of the 
simple membrane of the mucous system. I 
am familiar with many of the appearances on 
which it is founded, and without presuming to 
pronounce them very decidedly deceptive, I 
may state that hitherto my observations induce 
me to agree with Dr. Baly{ in his rejection of 
the interpretation put upon them by the Ger- 
man anatomists. A thin slice of a mass of the 
many-lobed terminal vesicles of one of these 
glands, especially if compressed, very readily 
assumes the aspect of a congeries of cells, each 
entirely surrounded by an envelope of base- 
ment membrane. But I have several times, in 
favourable sections, observed this membrane 
passing off into a neck, and becoming con- 
* Miiller’s Archiv. 1839, p. xlv. 
+ De digestione nonnulla. Berol. 1839. 
¢{ Translation of Miiller’s Physiology, p. 504. 
