Turner, MorpJiology of the Aviai/ Brain. 71 



In the reptilian brain Professor Herrick has considered 

 this zone to be an area of great proliferation — an area in 

 which cortex cells are developed. (') In birds it may have 

 a similar function. 



Minor nidulus. — In the basi-occipital lobe, near the 

 meson, and about half way way between the dorsal and 

 ventral surfaces of the hemisphere, there is a small, dense, 

 ellipsoidal cluster of cells. I have called this cluster the 

 minor nidulus. From this nidulus, the major axis of which 

 is perpendicular to the major axis of the hemisphere, a tract 

 of fibres passes to the anterior commissure (Plate VI, Fig. i^). 



Corf us str latum. — The remainder of. the axial region of 

 the prosencephalon constitutes the corpus striatum. (-) 



Histologically, the striatum is divided into two portions, 

 the striated portion and the caudate portion. In position, 

 these parts might be compared, respectively, to the lenticular 

 and caudate nucleus of the mammalian striatum. I am not 

 sure that these are true homologies, yet, as is stated below, 

 there are two fibre layers which might, perhaps, be consid- 

 ered homologues of the internal and external capsules. 



Striated portion (Plate VI, Fig. 8). — This portion lies in 

 the ventral part of the prosencephalon and is adjacent to the 

 crura cerebri. Passing from the crura cerebri into the cere- 

 brum, we meet three divisions of the striated portion of the 

 striatum: 



I. A narrow band of dense clusters of Deiter's corpuscles. 

 This band is, approximately, perpendicular to the entering 



1 "The great bulk ol tht axial lobe — the portion which protrudes into the ventricle 

 — is filled with similar flask cells, but these are curiously clustered in groups of two or 

 multiples of two. The evidence that these cells are undergoing rapid increase by frssion 

 in this young animal is very conclusive. All stages of the process may be observed. It 

 may be suggested that, if m the case of young animals this part of the brain is most 

 actively multiplying cells, it is possible that the growth of the mantle (in which there is 

 little material for rapid growth may be in some way associated with this proliferation of 

 cells, resulting in the increase of the mantle from its margins, as though the material 

 were pushed up around the margin of the ventricle by a rapid growth within." Op. 

 cit., p. 143. 



-» A. Bu.M.vi regards the whole of the asial portion of the- lirain as the lioiiioloiJiir of 

 the corpus striatum. Op. cit., p. 455. 



