Volltext: The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins (2)

most complicated glands he relied solely on 
his vascular injections, to the exclusion of the 
evidence afforded by the much more satisfactory 
researches of comparative and developmental 
anatomy. If, as Professor Miiller has ob¬ 
served, Ruysch had carefully examined his 
injected organs with the microscope, he would 
have found that between the most delicate 
plexuses of the bloodvessels there is always 
an additional substance destitute of vessels ; 
although these organs, when seen by the naked 
eye, appear to be stained in every direction 
with the coloured injection.* But even ad¬ 
mitting what frequently happens from a too 
forcible injection, that the matter thrown into 
the arteries is found in the ducts, this does 
not prove that the small bloodvessels are con¬ 
tinuous with the excretory canals; for after 
the sanguiferous vessels are filled, they easily 
become ruptured, and so allow their contents 
to escape into the ducts. It may further be 
objected, that in all the glandular organs which 
have been carefully inspected the commence¬ 
ments of the excretory ducts are larger than 
the least arteries ;f indeed, Ruysch’s own 
account of this imaginary continuity is very 
vague, and the plates designed to illustrate 
his theory, especially that of the kidney, are 
any thing but satisfactory. As Ruysch did 
not employ the microscope, it is impossible 
he could have seen that continuity which he 
so confidently described; indeed, as Ilaller 
remarks,X it is difficult, or rather as we should 
say impossible, to demonstrate, with the aid 
of the most powerful lens, the connexion of 
the last arteries with the coats of the ducts. 
Not only did Ruysch adopt a most in¬ 
sufficient mode in prosecuting his inquiries, 
but he assumed as a fact what was in reality 
a mere hypothesis, that secretion can only take 
place from the open mouths or orifices of the 
secerning arteries. The only point, therefore, 
which he discussed was, whether the passage 
of the arteries into the excretory ducts takes 
place gradually and insensibly, or suddenly 
and by the intervention of a follicle; for it 
never occurred to the anatomists of those times, 
or even to Haller and his contemporaries, that 
canals closed at their end by cul-de-sac, and 
without open arterial mouths, could secrete.§ 
* Loc. cit. p. 8, § 4. 
t Diameter of secreting canals. 
Parotid gland . . . 0-0099 (Weber). 
Kidney .... 0'0166 (Meckel). 
Ditto.....0-0180 (Weber). 
Testis .... 0 0564 (Miiller). 
Ditto..... 0-0648 (Lanth). 
Liver (in rabbits) . . 0 0140 (Miiller). 
Diameter of capillary bloodvessels. 
Line Line 
Parotid . . 0 0030 to 0-0039 (Weber). 
Kidney . . 0-0044 to 0-0069 (Müller). 
Testis . . . 0-0030 to 0-0035 (Weber). 
Burdach Physiol. Fünfter Band. p. 38. For 
measurements in other glands, see Müller De 
Gland. Struct, p. 112 ; Valentin Handb. der En- 
twickelungs-geschichte, p. 535 et seq. 
t El. Phy. t. ii. p. 378. 
$ The existence of open mouths in the arteries 
of the serous membranes, where they are generally 
But the true opinions of Malpighi did not 
refer to the exact mode of termination pos¬ 
sessed by the arteries; nor did he imagine 
that any particular machine or follicle was 
interposed between the arteries and the ducts : 
his observations were rather directed to the 
more important circumstances relative to the 
disposition, formation, and extent of the true 
secreting canals. 
In concluding these remarks on the hypo¬ 
thesis of Malpighi, it is due to the character 
of that illustrious cultivator of anatomical sci¬ 
ence to state that his views are highly phi¬ 
losophic, and in a general manner correct— 
that they are supported by numerous obser¬ 
vations made on the glands of the lower ani¬ 
mals, as well as on the development of the 
liver during incubation—and that he had thus 
the sagacity to adopt the mode, which expe¬ 
rience has shown is alone capable of resolving 
this difficult question. 
It would be superfluous to enter into a de¬ 
tailed account of the opinions advanced by 
later anatomists, as they are for the most part 
simply modifications of the hypothesis either 
of Malpighi or of Ruysch. A few general 
observations will therefore suffice. 
Ferrein has the merit of being the first wri¬ 
ter who pointed out in a more distinct manner 
than had been done by Malpighi, the great 
importance of what are erroneously called the 
excretory duets, but which constitute, as we 
have already shown, the true secerning struc¬ 
ture. He remarks * that the cortical part of the 
kidney is composed of a collection of white 
cylindrical tubes, variously folded on them¬ 
selves (canales corticales, or ducts of Ferrein,) 
and he thought he had seen the same tubes in 
the liver. The serpentine cortical canals have 
been seen in birds by Galvani, to be filled with 
cretaceous urine after the ligature of the ureter. 
Although the researches of Ferrein are very 
important, yet they want that support from 
comparative anatomy, by which means alone 
they could have been made subservient to esta¬ 
blish any general principles. 
To Rolando belongs the honour of having 
demonstrated the mode in which the glands 
are developed from the alimentary canal. By 
carefully conducted observations on the in¬ 
cubated egg, he discovered that each of these 
organs in the first instance consists of an ele¬ 
vation or tubercle of the intestine, which sub¬ 
sequently becomes hollowed and forms a canal 
directly continuous with that of the intestine. 
He also distinctly announced what has since 
been demonstrated in all its details, that the 
lungs are formed, like the glands, by a pushing 
out of the upper end of the intestinal tube; 
and he further describes the mode in which 
the bronchi and their subdivisions are deve¬ 
loped. The error of those writers who contend 
called exhalants, has never been proved ; on the 
contrary, on examining, with a powerful micro* 
scope, the circulation of the peritoneum in rabbits, 
I have repeatedly observed that the small arteries, 
after ramifying in a very complicated manner, 
become distinctly continuous with the little veins. 
* Mem. de l’Acad. Roy. des Sc. 1749 p. 492 '


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