68 
MR. BOWMAN ON THE STRUCTURE AND USE OF 
(fig. 9). When size and vermilion are employed, this is very apt to occur* *, and 
especially when the specimen injected is not fresh ; for the epithelium soon loses its 
adhesion to the basement tissue of the tube, and, falling into the cavity, mingles with 
the stream of injection, and renders its course obscure. This lining of the tubules 
with a pavement of epithelium occasions a striking appearance in perfectly fresh spe- 
cimens, when filled with double injection. This penetrating material insinuates itself 
into the interstices of the epithelial particles, and thus marks them out as a kind of 
pattern on the wall of the tube. When extravasation does not take place in the 
Malpighian bodies, more or less of the network surrounding the tubes is not unfre- 
quently injected. The most perfect specimens of injected Malpighian tufts are then 
obtained ; but the veins themselves are seldom well filled through the arteries, for not 
only is the way to them circuitous, and broken up into a thousand separate avenues 
(the Malpighian tufts), but it is usually loaded with blood. When injection is driven 
into any one branch of the renal artery, the several states now detailed are seen 
only in the parts to which that branch is distributed. There is no anastomosis be- 
tween the branches in the interior of the gland. 
It sometimes happens that in injections by the artery, extravasation is found to 
take place into the interstices of the tubes, with or without escape into the Malpighian 
capsules and tubes. This may arise from rupture either of the arterial tree, before 
reaching the Malpighian bodies (which is uncommon, where great force is not em- 
ployed), or of the efferent vessels of those bodies, or of the network of the tubes, 
injected through them. It may also occur from rupture of a tube, which has been 
itself filled by the rupture of a Malpighian tuft. 
By the Veins, the Capillaries surrounding the tubes may be injected, but neither the 
Malpighian bodies, nor the arteries, nor, without extravasation, the tubes. 
The capillaries of the uriniferous tubes are of great aggregate capacity, and com- 
monly contain much blood. When injection is pushed into the vein the whole organ 
instantly swells ; so rapidly do these dilatable and freely inosculating channels 
receive the fluid impelled into them. By the numerous communications of the capil- 
laries with the veins, it is at once dispersed in every direction, and enters the capil- 
however, that these bodies are unconcerned in the train of morbid phenomena. They unquestionably are so, 
and even necessarily must be so, from their anatomical structure, but in what manner I shall not at present 
attempt to show. 
* My friend Mr. Quekett, of the College of Surgeons, possesses many very excellent specimens of in- 
jected kidneys, in many of which he has been able to detect the tube passing from the Malpighian body, 
since his attention was directed to this arrangement. He also showed me a very beautiful injection of the Mal- 
pighian bodies in the Horse, sent over to the Microscopical Society of London by Prof. Hyrtl of Prague. In 
one comer of this we found a similar extravasation, though the disposition in question seems to have eluded the 
attention of that excellent anatomist. I am indebted to Mr. Quekett for some finely injected specimens of a 
boa’s kidney, from one of which fig. 14. is taken. 
