Ti'RXEK, ^forp]ioloi:;y of tJic Avian Brain. 6-^ 



Omitting the lenticular nidiilus and lobe, I have found in the 

 bird brain homologues of all the mantle niduli and lobes 

 described in Prof. Herrick's paper. 



Divisions. — For convenience the mantle has been divided 

 into two divisions, a mesal and a lateral division. The niesal 

 division is that portion of the mantle which lies mesad of 

 the lateral ventricle. The remainder of the mantle consti- 

 tutes the lateral division. Each division contains three lobes. 

 In describing these lobes, I shall begin at the cephalic extrem- 

 ity of the mesal division and pass caudad through the mesal 

 to the lateral division. Then I shall turn and pass cephalad 

 through the lateral division to the starting point. 



Pronto-median Lobe. — This lobe constitutes the cephalad 

 portion of the mesal division of the mantle. It is the devel- 

 opment of this lobe that causes the cephalad portion of the 

 ventricle to be diverted from the meson. (Plate \"I, Figs. 

 3, 5; F. M. L.) The ental boundary of this lobe is formed 

 by the lateral ventricle; the mesal boundary is formed by the 

 fissura longitudinalis; the dorsal portion of the cephalad 

 boundary is formed by the frontal lobe, while the ventral 

 portion of the same boundary is at the cephalad extremity of 

 the prosencephalon. Near the dorsal surface of the hemis- 

 phere a projection of the frontal lobe is wedged in between 

 the fronto-median lobe and the meson. 



Form and Size. — This lobe is about twice as long as its 

 greatest width and both horizontal and transverse sections of 

 it are sub-triangular in outline. Dorsad and cephalad the 

 lobe is quite wide, but while passing entad it becomes very 

 narrow . 



Near the dorsal surface of the brain the narrow caudad 

 portion of the fronto-median lobe fuses with the narrow 

 cephalad portion of the occipital lobe. Thus we have a nar- 

 row neck connecting two larger areas. (Plate VI, Fig. 3.) 

 Ventrad to this neck the fronto-median lobe is connected by 

 a narrow strip of biain substance t<,) the intraventricular 

 lobe. 



