ANATOMY IX A NUTSHELL. 439 



LESSON CXXX1Y. 



Fourth Ventricle. 

 The ruof or posterior boundary Is formed by the cerebellum and has the 

 following points for consideration: 



1. Superior peduncles of cerebellum. See page 354 



2. Valve of Vieussens, anterior or superior medullary velum. 



3. White matter of vermiform process of cerebellum. 



4. Inferior medullary velum. 



5. Epithelial lining of choroid plexus. 



6. Tela choroidea inferior. 



7. Obex. 



8. Ligulse. 



The floor or anterior boundary is formed by the pons and medulla and has 

 the following points for consideration: 



1. Eminentia teres. 



2. Fovea superior. 



3. Conductor sonorus. 



4. Locus caeruleus. 



5. Fovea inferior. 



6. Ala cinerea (trigonum vagi.) 



7. Trigonum hypoglossi. 



8. Tuberculum acusticum. 



LESSON CXXXV. 

 The first cranial nerve is called olfactory. It leaves the cranium through 



the cribriform plate of the ethmoid. One disease of this nerve is called anosmia. 

 The second cranial nerve is called optic. It leaves the cranium through the 

 optic foramen. One disease of this nerve is optic neuritis. 



The third cranial nerve is called motor oculi. It leaves the cranium through 

 the anterior lacerated (sphenoidal) fissure. Paralysis of this nerve will canst 1 

 ptosis. 



The fourth cranial nerve is called trochlear. It leaves the cranium through 

 the anterior lacerated (sphenoidal) fissure. Paralysis of this nerve will cause 

 diplopia. 



The fifth cranial nerve is called trifacial. The ophthalmic division Leaves 

 the cranium through the sphenoidal fissure. This division of the nerve is sub- 

 ject to malarial and septic poisons. The superior maxillary division Leaves 

 the cranium through the foramen rotundum. The inferior maxillary division 

 leaves the cranium through the foramen ovale. These last two divisions are 

 subject to rheumatic influences. The fifth nerve is involved in tic-douloureux, 

 neuralgia, and toothache. 



The sixth cranial nerve is called abducens. It leaves the cranium through 

 the anterior lacerated (sphenoidal) fissure. Paralysis of this nerve will cause 

 convergent squint. 



The seventh cranial nerve is called facial. It starts to leave the cranium 

 through the internal auditory meatus and after passing through the aqueduc- 



