134 



FIRST LE880N8 IN ZOOLOGY. 



aa-- 



--ia 

 bat 



Aran 



anus, immediately in front of the urinary and . genital apertures. 

 The liver (Li) forms an elongated light-brown mass resting upon the 

 stomach. The elongated gall-bladder lies between the liver and 



stomach, somewhat imbedded in the 

 substance of the former. There is no 

 pancreas, though it is present in some 

 fishes. The spleen (8p) lies between the 

 stomach and intestine, in the mesentery; 

 it is dark reddish-brown in color. 

 The air-bladder (S) is a single large 

 -djM glistening sac, placed in the dorsal part 

 of the body-cavity. The air-bladder 

 normally contains only gases. It con- 

 --iiA ceals most of the kidneys, which extend 

 the whole length of the body- cavity on 

 either side of the middle line, as two 

 long, wide strips of a deep though dull 

 red. They project beyond the air-blad-. 

 der in front (Ki) and behind (Ei). 



The ovary is single, and varies great- 

 ly in size according to the season. In the 

 male the sexual glands (testes) are 

 double. 



The heart {Ht) lies in the triangular 

 pericardial cavity; it consists of two 

 portions, the dark-colored venous cham- 

 ber, or auricle, above, and the lighter- 

 colored arterial chamber, below. The 

 auricle receives from above two large 

 veins, one from either side; these veins 

 are called the Cuvierian ducts. Fur- 

 thermore, a large vein, the sole repre- 

 FiG. 141.— Circulation of the blood j. .. » ., j? i,- i, 



in a bony fish, au, auriele; ven, sentative of the vena cam of higher ver- 

 ventriole; fcir, bulbus arterio- tebrates, passes from the liver, near its 

 sus; no, aorta; 6a, one of the .^ . , , , ., . ,. 



four branchial arteries which anterior end, through the pericardium, 



S'JS-ds'^.SSte to'S af «°d empties into the Cuvierian ducts 



descending aorta (dao); pc, por- near their common auricular orifice. 



^ndLfveM'cVena'cf^l'Na: The brain should be exposed from 



kidney. above by carefully removing by a knife 



the skin and thin bones covering the brain-cavity. Beginning in 



front, we notice the minute olfactory lobes and the olfactory nerves 



proceeding to the nasal cavities. Behind the olfactory lobes lie in 



succession the cerebral hemispheres (H), optic lobes (Q), tbe single 



cerebellum (CJ), and, lastly, the raedullH oblongata (in. 



