RAIA, 315 
spiracle and out over the gills. | Breathing is therefore 
independent of the mouth. 
If the skate be laid on its dorsal surface, and the skin 
and underlying muscle be removed in the area lying between 
the coracoid and pubic bars, the spacious abdominal cavity 
will be exposed. In it lie freely the other portions of the 
alimentary system. The esophagus entering the abdomen 
at the front end leads-into the large stomach, which is U- 
shaped and inclined to the left. It is mainly hidden by the 
spreading trilobed gland, the “ver, which is attached at the 
anterior part of the abdomen, but each lobe hangs free 
posteriorly. From the opposite end of the stomach to the 
cesophageal opening there arises the zzfestine, a tube of 
varying calibre passing down to the cloacal aperture. Its 
first portion, the dwodenum, is short and leads into the very 
wide z/ewm containing in its interior a sfzval valve. The 
last portion is the vectwm, narrower than the intestine proper 
and with no spiral valve. It opens into the cHaca. 
This alimentary canal has three important glands which 
open into it. The “Aver has already been referred to. 
Between its median and right lobes is a gad/-bladder, from 
which there passes a long Jdz/e-duct to open into the duo- 
denum. -The bile, secreted by the liver, is stored in the 
gall-bladder and periodically discharged into the duodenum 
by the bile-duct. Near the duodenum is a bilobed whitish 
organ of moderate size, called the pancreas. It secretes 
a digestive fluid which is discharged by a short pancreatic 
duct into the commencement of the ileum on its dorsal 
side. Lastly, near the termination of the rectum is a small 
oval rectal gland opening into the rectum; it may be excretory. 
Before leaving the alimentary system, the sp/een, a dark- 
red ductless gland near the stomach, should be observed. 
Note also the Jorta/ vez, a large vein draining the stomach, 
intestine, spleen and pancreas, and passing forwards to the 
liver; and the celiac artery which supplies the stomach, 
duodenum and liver with arterial blood. 
If the skin and muscles be removed from the area 
between the mouth and the coracoid bar, the gericardial 
cavity will be exposed. It communicates with 
the abdominal cavity by a pair of small canals, 
and the two cavities compose the perivisceral ccelom. They: 
Vascular. 
