Bauhaus-Universität Weimar

LACTEALS IN THE VILLI. 
271 
escape of the red particles of the blood from the capillaries. All 
good observers agree that there are no visible openings in the villi of 
the intestines; and I have myself repeatedly examined the villi of 
the intestines of the calf, ox, rabbit, hog, and cat, without having 
even perceived any perforation in their extremity. No opening 
certainly exists at that part of the villi. 
Structure of the intestinal villi.—The villi of the intestines are 
short processes, a quarter of a line to a line, or at most a line and 
two-thirds in length, rising from the surface of the mucous membrane, 
and giving this membrane, when magnified, the appearance of a 
thick fleece. Their form is sometimes cy lindrical, sometimes lamellar, 
and frequently pyramidal. 
Rudolphi at first believed that the villi were devoid of blood-vessels, 
and A. Meckel imagined that all the injection which entered them 
did so by imbibition or extravasation. Meckel could not have had 
before him good preparations of injected villi when he came to this 
conclusion. Not only can the vessels of the villi be beautifully shown 
by injection, as Doellinger, Seiler, and Lauth have described and 
represented, but I have, with the naked eye as well as with a lens, 
seen them filled with blood. Once I observed this in the calf, and 
' ‘A / 
afterwards in the dog, the intestine being examined immediately after 
death before it was washed. 
The extremity of the villi presents the same delicate texture as the 
rest of their surface. The assertion of Bleuland and others, that they 
had an opening at their extremity, was refuted by Rudolphi, who ex¬ 
pressed all that has hitherto been known of the structure of these 
parts in the following words:—“ They have never any visible open¬ 
ing; in their interior there is a network of blood-vessels, which can 
seldom be demonstrated, however, except by injection; and the 
lacteals also take their rise by a network within the villi.” 
It appears to me to be an important circumstance, that the villi are 
in part hollow, and are formed of an exceedingly delicate membrane 
in which blood-vessels ramify. The simple cavity I have found prin¬ 
cipally in the cylindrical villi. By comparison I have ascertained that 
the thickness of the membrane which forms the villi in the calf is 
-j4öth of an inch, and the diameter of the capillary blood-vessels 
which run in this membrane, may be reckoned at from -jy^th t0 
TsVoth of an inch. An opportunity occurred, recently, at the dis¬ 
secting-rooms in Berlin, of examining the villi of intestines in which 
the lacteals were filled with chyle in the human subject. They were 
found to contain a simple cavity running from base to apex. This 
was proved both by the microscopic examination of the villi by 
Henle, and by their injection with mercury by Schwann, who forced 
the mercury into the lacteals which were distinctly visible in the 
mucous coat, and thus filled the villi even to their closed extremity. 
There is something of a very different nature, which might be mis¬ 
taken for hollow villi. This is a kind of epithelium, but of extreme 
delicacy. It is not solid, like an epidermis; on the contrary, although 
coherent in a membranous form, it is so nearly allied to mucus, that 
it seems to me to be a secretion intermediate between epithelium and 
mucus.
        

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