Brain and Heart of Fishes. 



13. Internal organs of fishes. The brain of 

 fishes (fig. 9) is small, not filling the cranial cavity. 

 It consists of a succession of little knobs or ganglia 

 arranged in a chain from before backwards. Of 

 these the foremost are connected with the sense of 

 smell, the second consist 

 of the fore- brain hemi- 

 spheres or cerebrum, the 

 third are the optic lobes 

 from which the nerves of 

 sight arise, the fourth con- 

 stitute the mid-brain and 

 the fifth the hind brain. 



Beneath and behind 

 the head lie the gills (fig. 

 10), which consist of nume- 

 rous vascular fringes ar- 

 ranged in platelike layers 

 attached to the visceral 

 arches, and bathed by the 

 water which enters the 

 mouth and escapes through 

 the visceral slits. The heart 

 is situated in the middle Brain of Cod. 



Of What We might Call the /, nerves of sight; k, nerves of smell; 



. ... a, foremost lobe of brain ; c. se- 



throat, a Very Short distance cond lobe or cerebrum ; / cere 



u U' J it. i bellum; A, hind brain or medulla 



behind the lower jaw. oblongata ; , fifth pair of nerves ,; 



This nrain rnndstc; nf a , nerves of hearing ; 0, ninth pair 



>1SIS 01 a of nerves; /.tenth or vagus nerve. 



thin-walled auricle, receiv- 

 ing the veins which convey to it the impure blood 

 from the body, and a large thick-walled ventricle for 

 propelling the blood into the gills. This latter is 

 ca 



