186 PHOLADID. 
tion ensued, but not a particle of the mineral found a passage 
to the branchial vault ; this result occurred in many specimens, 
and though the pressure was often considerable before regur- 
gitation was allowed to take place, still the branchial division 
of the mantle remained free from the quicksilver. In one 
experiment the fluid appeared in the lateral tissues; this 
I attribute to a lesion of the dorsal lateral membranes. 
2ndly, I found that when there was not the slightest solution 
of continuity in the fine membrane on which the branchial 
vessels are fixed on one side, and the interweavings and 
traceries on the other, which form the roof of the anal siphon, 
the application of the mercury to that tube gradually filled 
the whole range of the branchial vessels, which exhibited a 
very elegant appearance, but no fluid escaped from them into 
the branchial sac. 3rdly, I repeated many times the first 
experiment with the view of endeavouring to find a passage 
through the rectum and intestine on the dorsal range that is 
embraced by the heart, but without success; if I had suc- 
ceeded, it would have been impossible to arrive at the stomach 
and mouth, as the intestine plunges into the body coasting 
the foot, at which point it is of larger diameter, and always 
filled with a compacted mass of sand which effectually stops 
up the passage: this part of the intestine around the foot, 
from its difficulty and the hardness of the fecal matters, 
seems analogous to the ascending portion of the colon in 
man. 
In all these attempts either regurgitation ensued, or the 
continual pressure of the mercurial column caused lesions. 
This impossibility to pass anything into the rectum pro- 
bably arises from its sphincter, or one in the anal tube, as 
the stoppage always occurred at that poimt where it empties 
into it. 
Athly, On applying the mercury through the mouth and 
cesophagus the stomach was readily filled; but as soon as the 
pylorus was passed, a stoppage not to be removed occurred, 
from the duodenum being, like the colon in the last case, filled 
with sand; we may therefore conclude that water can never 
enter the stomach of bivalves from the anal tube. 
