Chap. III.] GENERAL ANATOMY. 33 



has thinner walls. The stomach is bent upon itself, and where 

 it passes into the intestine there are a number of pyloric cceca 

 (Py. Cce.). A little beyond these processes is the common bile duct 

 (c. b. d.) formed by the confluence of hepatic ducts (h. d.) from the 

 liver. The cystic duct (c. d.) leading to the gall bladder (G. B.), 

 in which the bile is stored, is an offshoot from the common 

 duct. The intestine is somewhat coiled, and passes almost with- 

 out change of diameter to the anus (a.). 



2. The Respiratory System. The respiratory organs are the 

 gills which we have seen in the last chapter. There are no 

 lungs. 



3. The Heart and Circulatory System. To expose the heart the 

 hip-girdle must be divided in the mid-line and the upper half (in 

 the present position of the fish on its side) of both this girdle 

 and the shoulder-girdle carefully removed. The pericardial 

 cavity thus displayed is a small chamber lined with pericardium, 

 which is reflected over the heart. The heart itself has a thin- 

 walled dorsal sinus venosus (14 A, s. v.), an irregular thin-walled 

 atrium (cm.), not divided by any septum into two auricles, a 

 fleshy ventricle (v.) with a single cavity, and a whitish bulbus 

 arteriosus (b. a.). 



The bulbus arteriosus passes forward into the median ventral 

 aorta (14 B, v. ao.), which forthwith sends off branches, afferent 

 branchial arteries (af. br. a.), right and left to the four gills on 

 either side. In the capillaries of the gills the blood is aerated 

 and collects into vessels (efferent branchial arteries, ef. br. a.), 

 by which it is conveyed to vessels, one on each side, which 

 run along the dorsal ends of the gill-bearing branchial arches 

 (right and left epibranchial arteries, ep. br. a.). Traced forwards, 

 these run into the (carotid, car.) arteries which supply the head 

 and brain. They are united together by a transverse vessel 

 beneath the back of the skull (tr.). Traced backwards, the 

 epibranchials fuse together to form the dorsal aorta ; but before 

 they unite each gives off an artery (subclavian, s. a.) to supply 

 the pectoral fin, and that on the right side gives off in addi- 

 tion arteries (coeliac, CM. a., and mesenteric, me. a.) to supply 



