296 ANATOMY OF THE DOMESTIC FOWL 



the orbit, and pass through the olfactory foramina and in grooves 

 on the upper part of the septum; then passing forward they pene- 

 trate the frontal structure and are finally distributed over the 

 turbinated mucous membrane. 



The corpus striatum is large; it occupies nearly the entire floor 

 of the ventricles. 



The anterior commissure is foimd between the hemispheres. Its 

 middle part lies in the lamina terminaUs on the division between 

 the anterior and the middle brain, and close to the thalami optici. 

 Its side extensions are rounded masses called the nervi amygdales. 



The corpus callosum, quite rudimentary, lies on the posterior 

 dorsal rim of the anterior commissure. 



The corpus striatum forms a thin broad ridge, which passes ven- 

 trally. This structure consists of twenty-five large pjramidal cells 

 which He in the posterior lateral dorsal section, and of from ten to 

 fifteen pyramidal cells which are located in the rest of the section. 

 In addition to these two groups there are many cells about 5 milli- 

 meters in diameter. These he, six or more, in a nest imbedded in 

 neuroglia. There is a thin layer of spindle cells near the ventral hne. 

 The outer nerve nest, or nerves amygdalis, Hes in the' posterior 

 lateral ventral part. It is covered by a thin membranous layer. 

 Its cells are pyramidal in shape and are from 10 to 15 millimeters in 

 diameter. The cells terminate in spindle form toward the periphery. 

 Nerve fibers extend from the anterior commissure. 



The outer wall of the corpus striatum consists of the following 

 layers: 



An outer white layer consisting of fine meduUated nerve fibers 

 imbedded in a groimd substance containing numerous nerve cells. 



A layer of ganghonic cells, consisting of pyramidal cells from 10 

 to 15 millimeters in diameter, of other round cells 20 millimeters in 

 diameter, and finally of cells only 5 millimeters in diameter. This 

 layer forms a reddish line in the dorsal portion of the corpus striatum. 



These layers form part of the median and the posterior cerebral 

 wall of the lateral ventricle. The lateral ventricle is closed except 

 for a slit-like opening behind the posterior commissure. This is the 

 foramen of Monro, through which the lateral ventricle communi- 

 cates with the middle, or third, ventricle. 



The choroid plexus is found at the base of the lateral ventricle. 



The wall of the lateral ventricle becomes thinner near the region 

 of the transverse commissiu-e on the surface toward the middle 



