49 
Structure and Uses of the Spleen. 
but no venal ones, which confirms the statement of Malpighi ; 
and when the cells are empty and contracted, and the blood- 
vessels filled to a great degree of minuteness, the appearance 
of celk is entirely lost, as stated by Cuvier. 
When the cells were in a distended state, their cavities in 
a great many instances were very distinct, having been laid 
open in making a section of the spleen. The intermediate 
parts of the spleen are but sparingly supplied with arterial 
branches, and the smaller ones do not appear to have any 
particular distribution. 
When the veins only are injected their branches appear more 
numerous, and larger than those of the arteries, making the 
whole substance of the spleen of a red colour. They appear 
to arise from the outside of the cells going off at right angles 
to their circumference, like radii. Where the injection has not 
been very minute, they are seen to arise at so many points of 
the capsule ; but where the injection has got into smaller 
branches, their number is so much increased that they appear 
to form plexuses round the cells. 
The trunk of the splenic vein, compared with that of the 
artery, when both are filled with wax, is found to be in the pro- 
portion of five to one in its size. This was ascertained both by 
an accurate measurement of their diameters, and by weighing 
half an inch in length of each in a very nice balance ; the dis- 
proportion between them is greater, than between corre- 
sponding veins and arteries, in other parts of the body. 
Having acquired this knowledge of the internal structure 
of the spleen, I made the following experiment with a decoc- 
tion of madder. This substance was employed, from the 
animals who feed on it having their bones tinged red, so that 
there can be no doubt of its colouring matter being carried 
mdcccviii. H 
