36 POULTRY DISEASES 



The fissure lateralis is well marked and is located laterally 

 about the posterior border of the anterior third of the cere- 

 brum. The epiphysis, a small body, is located between the 

 hemispheres and at the posterior portion of the longitudinal 

 fissure. The olfactory nerve consists of two conical ])odies 

 projecting forward from between the anterior portion of the 

 hemispheres. The hypophysis (infundibulum), cruri cerebri 

 and optic chiasm are similar to those of mammals. The cor- 

 pus callosum is lacking or at most marked by only a few- 

 diagonal fibers. The hippocampus and the septum lucidum of 

 mammals are lacking. The lateral sinuses are well developed. 

 The lateral walls are thin and the grey matter small in quan- 

 tity. At the base of each of the sinuses there is found an 

 eminence which corresponds to the corpus striatum of mam- 

 mals. At the postero-inferior portion of the cerebral hemis- 

 pheres there are rounded eminences called the sight emi- 

 nences. They are bounded on the dorsal side by the bridge 

 of Sylvius. Their cavity communicates with the aqueductus 

 cerebri which connects the third and fourth ventricles. 



The cranial nerves number twelve, as in mammals. The 

 olfactory (first cranial nerve) leaves the cranial cavity 

 through a foramen which represents the perforated plate of 

 mammals. It passes through the dorso-median part of the eye 

 cavity, thence into the nasal cavity, where its fibers terminate 

 in the mucous membrane. 



The optic nerve (second cranial) forms the chiasm at the 

 base of the brain. At this X the two nerves of sight cross. 

 The motores oculorum (third cranial), the pathetici (fourth 

 cranial), and abducens (sixth cranial) are distributed to the 

 muscles of the eyeball. The trifacial (fifth cranial) gives off 

 three branches, the ophthalmicus, the maxillaris and the man- 

 dibularis. The branch corresponding to the lingual of mam- 

 mals is lacking. The facial (seventh cranial) is not well de- 

 veloped. The auditory (eighth cranial) extends into the 

 labyrinth of the ear. The glosso-pharyngeal (ninth cranial) 

 gives off a branch extending to the tongue ; the remainder of 

 the nerve is distributed similar to that in mammals. 



The vagus (tenth cranial) and the spinal accessory (elev- 

 enth cranial) intertwine themselves in the proximity of the 

 skull. The course and distribution of the vagus is similar to 

 that in mammals. The hypo-glossal (twelfth cranial) is the 

 motor nerve of the tongue. 



The cerebellum or lesser brain is located in liie posterior 

 part of the cranial eavit.y. Numerous oblique fissures mark 

 the upper surface, dividing it into a leaf-like structure. The 



