80 ANATOMY OF VERTEBRATES. 



called ( pineal ' and ( pituitary ' h, glands : a second pair of gangli- 

 onic masses are developed in Mammalia behind the optic lobes, o, 

 and received from the old anthropotomists the name of ( testes,' 

 the more constant and important pair being the f nates,' and the 

 whole, from their arrested condition in Man, forming the ' corpora 

 ( quadrigemina ' or ( bigemina.' 



The third primary division of the brain includes the ( crura 

 cerebri ' with the reinforcing or recruiting ganglions called 

 ( thalami optici ' and ' corpora striata,' and the superincumbent 

 masses called ( cerebral hemispheres : ' it is the e prosencephalon,' 

 figs. 46 and 47, P. 



The foremost primary division of the brain includes the anterior 

 termination of the columnar tracts, called ' crura rhinencephali,' 

 and the appended vesicular mass, called ( olfactory lobe ; ' it is the 

 6 rhinencephalon,' ib. R. The nature and value of this division 

 are masked, in Man, by the arrest of its developement and the 

 contrast of the excessive expansion of the vesicular part of the 

 antecedent division. Accordingly the ( crura rhinencephali ' are 

 termed ( olfactory nerve ' with its ( roots,' and the primary vesicle 

 is the ' bulb of the olfactory nerve,' of anthropotomy. 



Each primary encephalic division has its cavity or cavities 

 called ' ventricles.' The epencephalic prolongation of the mye- 

 lonal canal is the ( fourth ventricle :' its continuation into the 

 primary vesicle is the ( cerebellar ventricle :' it is persistent in 

 fishes (vol. i. p. 275, fig. 178, c\ reptiles (ib. p. 295, fig. 193), 

 and birds (vol. ii. p. 120, fig, 45), but is obliterated in Mammals 

 where the cerebellum is solid. The ' myelonal canal ' passes for- 

 ward as the ' third ventricle,' and ' iter ' or communicating canal 

 between that and the ' fourth.' Its continuation into the optic 

 lobes, retained in oviparous Vertebrates (vol. i. p. 278, fig. 182, 

 h, b, p. 279, fig. 183, d, p. 295, fig. 193, 3, vol. ii. p. 120, fig. 45, 

 o,) is obliterated by growth of neurine in Mammals ; as is also its 

 ascending canal to the ' pineal appendage ; ' the descending one 

 to the ( hypophysis ' is retained as the ' infundibulum.' 



Each cerebral hemisphere begins in Mammals, as in lower 

 Vertebrates, as a bladder with a thin wall of brain-substance, the 

 cavity including, potentially, all the anthropotomical 'horns,' ' fore,' 

 6 aft,' and 'under,' of the 'lateral ventricle,' which are subsequently 

 meted out by endogenous growths of grey and white neurine, in 

 size and shape according to the group or genus. 



In most Mammals which derive so important a share of their 

 ideas through the olfactory sense, the ' lateral ventricle ' is con- 



