20 



G. Cut open the nasal sac and note the folds formed by the mucous memhrane; the 



folds lie parallel to each other and at right angles to a longitudinal median 



ridge. 



H- Carefully cut away from above, in thin slices, the cartilage of the left auditory 



capsule, and expose the membranous labyrinth, noting — 



(a) The large rounded vestibule with its two depressions fiUed with endo- 



lymph. 

 (6) The aqueductus vestibuli leading upwards from the vestibule to the exterior; 



(c) The anterior and posterior, and the lateral horizontal semicircular canals, 



and the three ampuUse. 



(d) The large soft otolith lying in the vestibule. 



Note the distribution of the Vlllth. nerve to the vestibule and ampullae. 

 Make a diagram showing the vestibule, semi-circular canals, and the aqueduct. 

 I. Circulatory system. 



1. Eemove the abdominal wall to expose the viscera, slightly stretch the 



mesenteric membranes, and note — 



(a) The portal vein in the duodeno-hepatic omentum, — observe that it is formed 



by the gastric, duodenal, intestina], splenic and pancreatic veins, and 

 that it passes to the middle lobe of liver, giving off branches to the right 

 and left lobes. 



(b) The coeliac artery arising from the aorta, on the dorsal side of the oeso- 



phagus, and dividing into gastric, hepatic, and duodenal arteries. 



(c) The superior mesenteric artery, arising from the aorta posterior to the cceliac, 



and dividing into intestinal, splenic, and pancreatic arteries. 

 Mark these arteries by inserting bristles, and then cut out the liver to within half 

 an inch of its anterior end, so as not to injure the hepatic simis (for descrip- 

 tion see 10, p. 22), or the alimentary canal. 



2. Examine (low and high power) a drop of the blood, noting the large oval 



nucleated red corpuscles, and the smaller multi-nuclear white corpuscles. 



3. Eemove the ventral wall of the pericardial chamber in front of the pectoral 



girdle within the line of the branchial clefts, noting the pericardium and 

 the pericardial fluid and the opening, in the middle line, of the pericardial 

 chamber which leads into the two canals (pericardio-peritoneal) that bring 

 the pericardium into communication with the abdominal cavity. 



4. Examine the heart, noting — 



(a) The semicircular sinus venosus. 

 (6) The thin-walled auricle. 



(c) The thick muscular ventricle. 



(d) The pylangium (conus arteriosus), extending forwards from the ventricle. 



(e) The synangium (bulbus arteriosus), anterior to the pylangium. 



