412 PROCEEDINGS OF THE CANADIAN INSTITUTE, 
separates the fibres into bundles. Both muscular coats may at posi- 
tions quite change their directions, so as to leave it doubtful if there 
is more than one coat. Fibrous connective tissue enveloped these 
on the outside, and on this again is superposed the mesentery. The 
mucous coat contains coarse connective tissue fibres and has imbedded 
in it numerous arterial branches which divide and rise under the 
epithelium layer. Very few lymph corpuscles were observed. 
Beneath the epithelium the fibres become arranged more densely 
and give the appearance of a muscularis mucosae. They form a 
basement on which the epithelium sits. This stratum of densely 
arranged fibres runs up into minute ridges in which small arterial 
capillaries and venous capillaries anastomose. 
The epithelium consists in the main portion of the bladder of 
long cylinder cells, slender, but of larger transverse diamete1 in its 
mouth and in the cystic duct. The protoplasm is very finely granular 
and surrounds a large oval nucleus. The outer peripheral border, 
easily lost in reagents, does not possess the striation that Virchow' 
describes for other vertebrates. The basal processes are very slender, 
often divide into two or more branches, and interlace with the fibres 
of the mucosa. 
In the main portion of the gall-bladder there are but few glandular 
follicles or crypts. In the arched portion of the duct of the bladder 
they are much more numerous, and a few may be of such length that 
a portion of it is bent so as to be parallel with the mucous layer. 
The cells lining them are cylindrical or rather columnar, which in 
sections never exhibit a peripheral border, at least it is not manifest 
in fresh. A cross section of the tubules very often reveals slimy 
masses in the lumen. The cells do not differ otherwise from those 
of the general surface, and may have each a peripheral border like 
them. 
THE PANCREAS. 
For nearly halt a century before 1873 the presence or absence of 
a pancreas in the Teleost fishes had been one of the disputed ques- 
tions among anatomists. It may be convenient to go briefly into the 
history of this dispute, as it led to the discovery ultimately of a true 
pancreas. 
1 Virchow’s Archiv, Bd. XI., page 574. 
