24 
DR. C. H. JONES ON THE STRUCTURE, DEVELOPMENT 
celloid particle may rapidly decay, but a cell with a well-marked envelope is destined 
to a longer life ; its contents are as it were locked up. In such cells too, when the 
seeretory act is ended, the nucleus disappears, and the cell is henceforth only a repo- 
sitory of the product. This type of secretory action is, compared to the other, 
gradual and slow. But if a nucleus remain as such, if it exert an unceasing energy, or 
at least retain the power to exert that energy at intervals, if instead of developing a 
single cell, filling it with secretion, and then perishing, it continue to attract, to 
change and to repel charged matter, then we have a structure whieh is adapted for 
continuous, and, it may be, rapid action. This we have much reason to believe is the 
case in the instances of the thyroid and of the biliary ducts. 
I might also refer to the case of the intestinal villi during absorption, which is a 
rapid and temporary process ; the nuclei seem to attract the chyle into the villus ; thev 
do not develop cells wherein to enclose it, but allow it straightway to flow off by the 
lacteals, while themselves unchanged continue to attraet fresh matter. 
1 believe then the two conditions of the ultimate ducts to be essentially similar, 
differing only in the more or less quantity of granulous matter, by whose disintegra- 
tion in each case the material of the secretion is furnished ; the presence of the 
vesicles in the ducts so often mentioned, seems to me strongly indicative of active 
growth, though less rapid, and by consequence of change and decay ; and thus cor- 
roborates decidedly the view I have expressed. 
Once I have seen the nuclei of the ultimate ducts deeply bile-tinged ; this was in 
the liver of a Squirrel (Sciurus) , where many of the parenchymal cells also contained 
bile; this also seems to indicate an attractive power resident in them; it was 
remarkable that some duets were not thus coloured, and in these the nuclei were 
less elongated, were plumper, more healthy and vigorous-looking, to use a metapho- 
rical expression. The gall-bladder was nearly empty’^, and the condition, I suppose, 
was one of sluggish action of the ducts ; hence impletion of some of the parenehymal 
cells with bile, and staining of the nuclei of the ducts with secretion not thrown off. 
Those unstained were doubtless efficient and active. 
As it appeared to be matter of great importance to ascertain whethei the paien- 
chyma of the liver really contained bile, that is, not only the eolouring matter of the 
secretion, but its organic salts also, I applied to my friend Mr. Lindsey Blyth, who 
most kindly undertook at my suggestion a series of experiments to endeavour to 
decide the question. I may remark, that in the case of the liver there is far more 
reason to expect that its secretion should be capable ot being detected in its substance, 
than there is in that of the kidney ; urea cannot be found in the renal parenchyma, 
probably because it is so rapidly and completely carried out of the tubes of which it 
consists, and which present only an extremely thin layer of epithelium to be traversed 
in its transit from the blood into their cavity. But in the liver, the bile, if it exist 
