TifRNEu, Morphology of the Avian Bra'n/. 283 



nuclei-bearing sheath. Deiter's corpuscles are small cells, 

 which contain so small an amount of protoplasm that ordi- 

 nary preparations reveal only their nuclei. These minute 

 cells are universally distributed. The remaining three types 

 are encountered throughout the brain; but in anyone nidulus 

 some one type always predominates, often to the exclusion of 

 the other two. The flask cells resemble a flask in shape, and 

 when stained each cell presents a faintly stained nucleus, 

 within which is a densely stained nucleolus. Such cells are 

 supposed to be sensory in function. The pyramidal cells are 

 sub-pyramidal in outline. These cells stain densely, when 

 each one presents a densely stained nucleus, within which is 

 a densely stained nucleolus. Such cells are probably motor 

 in function. The multipolar cells resemble distorted, many- 

 branched pyramidal cells. Such cells probably act as switch 

 stations for nervous energy. 



EXPLANATION OF PLATE XVIIL 



Fig. 1. Transverse section of the brain oi Hylocickla Szuainsona, 

 taken through the root ganglion ot" the auditory nerve; a., tractus B of 

 the seventh and eighth nerves; B, nidulus B of the seventh and nerves; 

 d, nidulus d of the seventh and eighth nerves; Sg, root ganglion of the 

 auditory nerve. 



Fig''- ..', ■', 4, <5- Transverse section of the metencephalon of Sialia 

 sia/is; \', root of fifth nerve; I'l//, root of seventh and eighth nerve. 



Fig. I). Section through the cortex of the epencephalon. 



Fig. 8. Horizontal -longitudinal section through the fifth nerve 

 root of Hylocichla Sxvainsoni ; IV, root of trochlear nerve; V^, lateral 

 sensory root of the trigeminal nerve; -5^, lateral motor nidulus of the 

 trigeminal nerve; .5*, lateral sensory nidulus of the trigeminal nerve. 



Fig. .9. Horizontal longitudinal section through the metencephalon 

 of the domestic turkey brain, taken through the tenth nerve root; Jf, 

 tenth nerve root; !>, nidulus of the ninth nerve; 10, nidulus of tenth 

 nerve. 



Figs, JO-lJ. Successive transverse sections of the metencephalon 

 of Hylocichla Stvainsoni; a. tractus B of the auditory nerve; B, nidulus 

 B of the seventh and eighth nerves; d, nidulus Y of the seventh and 

 eighth nerves; V, root of the trigeminal nerve; VI, root of the abducens 

 nerve; 7^ nidulus B of the seventh and eighth nerves; '.), nidulus of the 

 ninth nerve. 



Fi.gs\ 1S'14- Transverse section through the metencephalon of 



