ZQO ANATOMY OF THE DOMESTIC FOWL 



the front part of the long furrow of the spinal cbrd there is observed 

 the third pair of cranial nerves, which have their origin in the middle 

 brain. The fourth pair of cranial nerves extend from the roof of the 

 middle brain on both sides between the middle brain and the optic 

 lobes. These nerves finally emerge and become visible on the 

 ventral surface. 



The sixth nerve is visible near the middle furrow and almost in 

 the middle of the pjramids, and near the roots of the fifth, the 

 seventh, the ninth, the tenth, and the twelfth pair of cranial nerves. 



THE DIVISIONS OF THE BRAIN 



Thalamus 



Pineal body 



Infundibulum 



Hypophysis 

 Forebrain Optic tract and chiasm 



Cerebral hemispheres 



Olfactory lobes 



Third ventricle 



Lateral ventricles 



Peduncles of the cerebrum 

 Midbrain Optic lobes 



Aqueduct 



' Medulla oblongata 

 Hindbrain Cerebellum 



Fourth ventricle 



The medulla oblongata (Fig. 62, No. C, i; Fig. 75, A and C) termi- 

 nates anteriorly in the pars commissuraUs and the pars peduncularis. 

 As the spinal cord approaches the head there is a gradual swelling, 

 or. lateral thickening, which merges into the medulla oblongata. 

 The superior and the inferior surface of the medulla oblongata (Fig. 

 75, No. ^, I and C, 17) are flattened. There is a shallow furrow and a 

 shght swelling at the point where the hypoglossal nerve emerges. 

 The central canal of the spinal cord gradually comes closer to the 

 upper surface and communicates with the fom-th ventricle, at which 

 point the posterior raphe is shortened and the sulcus longitudinalis 

 posterior becomes shallow. At the point where the central canal 

 terminates in the fourth ventricle there is a V-shaped point called 

 the calamus scriptorium (Fig. 75, No. 2). The fourth ventricle is 

 located on the upper wall of the medulla oblongata below the cere- 

 bellum, and is bounded laterally by the peduncles of the cerebellum. 

 It is marked posteriorly by the calamus scriptorius and anteriorly 

 by the valve of Vieussens. 



