50 MR. T. J. PARKER ON THE INTESTINAL 
§ 2. The most convenient method of preparing the intestine for examination is to 
distend it, after washing out the contents with a stream of water, with a 0°5-per-cent. 
solution of chromic acid, and then to place it in a vessel of the same fluid for a few days. 
By this method the walls become thoroughly hardened, so that windows can be cut in 
them to any extent without danger of collapse, and the whole extent of the valve 
examined in a perfectly natural position, At first I adopted the plan of distending the 
washed intestine with air, and then drying it; but experience proved that this method 
was almost worse than useless. ; 
§ 3. The esophagus of Raia enters the abdominal cavity in its antero-dorsal region, 
and almost immediately passes, with slight increase of diameter, into the stomach, 
This passes backwards, and slightly to the left, towards the posterior end of its cavity, 
and then, turning sharply round to the right, and undergoing a marked decrease of 
diameter, passes forwards to within a short distance of the anterior end of the abdomen, 
where it becomes constricted to form the pylorus. Beyond this point the alimentary 
canal immediately widens, forming the intestine; and this, becoming at once bent 
round to the right, passes at first directly backwards along the right wall of the 
abdominal cavity, and finally inwards, forming the rectum, until it reaches the middle 
line and dilates into the cloaca. Thus the intestine, or at any rate that part of it in 
which the spiral valve is contained (the valve-gut, Klappendarm), is practically a 
straight tube, and may be described as having an anterior and a posterior extremity, 
and dorsal, ventral, right, and left sides. 
The superior mesenteric artery passing to the right and somewhat ventralwards from 
the dorsal aorta, reaches the left side of the intestine a short distance posterior to the 
pylorus, and immediately passes straight backwards along the left or inner side to the 
rectum, the superior mesenteric vein running parallel with it. Both artery and vein 
send off, on each side, a set of branches nearly at right angles, in such a way that of 
each pair of branches one runs almost transversely along the dorsal side of the gut, the 
other in the same direction along its ventral side. The dorsal branch is, in every case, 
given off at a slightly more anterior line than the corresponding ventral branch; and 
the two branches, passing to the right, form an incomplete slightly oblique hoop round 
the intestine. The hoops thus formed, usually ten or eleven in number, correspond 
with the attachments to the parietes of the intestine of the successive turns of the 
spiral yalyes, with the single strange exception of the second, counting from the 
anterior end; this is seen, on opening the gut, to correspond to the middle of the 
space between the first and second turns of the valve. 
The portion of intestine anterior to the first branch of the mesenteric artery and vein 
is usually distinguished as the duodenal portion, or bursa entiana; it receives the bile 
and pancreatic ducts, and is supplied by a special (duodenal) branch of the ceeliac 
artery ; it differs, however, in no other respect from the remainder of the valve-gut. 
The portion of intestine posterior to the last branch of the superior mesenteric 
