DISSECTION OF THE HEAD AND NECK 



323 



I. Olfactory nerves (Nn. olfactorii). Do not confuse these with the 

 olfactory tracts. Try to find the fine threads of the Nn. olfactorii 

 penetrating- the ventral surface of each bulbus olfactorius. They 

 come from the nasal mucous membrane, through the lamina 

 cribrosa of the ethmoid bone. 



II. Optic nerve (N. opticus). It runs from the back of the eyeball to the 

 optic chiasm. The student's later studies will show him that the 

 optic nerve is really not a peripheral nerve, like the other cerebral 

 nerves, but rather a part of the central nervous system. 



Gyrus rectus 



\ 



FIG. 143. 



Fissura longitudinalis cerebri 



Trigonum olfactorium 

 N. opticus^ 



Chiasma opticum 

 Corpus mammillare 



Uncus (gyri hippocampi) v 



N. oculomotorius 

 Pedunculus cerebri 



Substantia perforata posterior 

 (Fossa interpeduncularis) T\ 



(Pons Varolii) 



N. trigeminus ~i_ 



N. abducens 

 N. facialis .. 



N. intermedius 



N. acustieus 

 N. hypoglossus 



Pyramis (medullae oblongatae) 

 Radix anterior N. cervicalis I. " 



Fissura mediana anterior 

 Decussatio pyramidum 



Tractus olfactorius 



Stria olfactoria medialis 



Stria olfactoria intermedia 



Stria olfactoria lateralis 



' Substantia perforata 

 anterior 



^ Tuber cinereum and 



infundibulum 

 Tractus opticus 



- - Sulcus n. oculomotorii 



^ Radix lateralis > tractus 

 ~~- Radix medialis) optici 



v Corpus geniculatum laterale 

 Fasciculus obliquus (pontis) 

 -^. Sulcus basilaris 



- Brachium pontis 



Foramen caecum 

 " Oliva 



Corpus restiforme 

 Fibrae arcuatae externae 



Sulcus lateralis anterior 

 Funiculus lateralis 



The medulla oblongata, pons (Varolii), cerebral peduncles, and part of the floor of the midbrain. 

 Seen from the basal surface. (After Toklt, Anal. Atlas, Wien, 1903, 3 Aufl., p. 765, Fig. 1174.) 



III. Oculomotor nerve (N. oculomotorius). Look for it in the fossa inter- 



pedunculnris. It belongs to the midbrain. 



IV. Trnclilear nerve (X. t rochlearis) . While all the other cerebral nerves 



emerge from the ventral aspect of the brain-stem, this nerve 

 emerges on the dorsal aspect. Its exact origin will be seen later. 

 Note that it is on the lateral aspect of the pedunculus cerebri, while 

 the oculomotor nerve is on the medial aspect of that structure. 

 V. Trigeminal nerve (X T . Irigeminus). 



(a) Larger portion (portio major], sensory. 



(b) Smaller portion (portio minor}, motor. 



