Anatomy of the Brain. 555 



position of this ganglion is the same as that occupied by the ear in 

 many of the invertebrates. That part of the restiform body which is 

 not concerned in the composition of the peduncles of the cerebrum 

 crura cerebri is turned backwards at right angles from the medulla ob- 

 longata at the pons varolii, and accompanies the fibres of the pons into 

 the cerebellum, and becomes the posterior peduncle of the cerebellum. 

 There is a heavy band of transverse fibres which passes across the an- 

 terior face ol the medulla oblongata just above the olivary bodies, which 

 is called the pons varolii. ( See figs. 266, 267, 272.) This band passes 

 on each side around the upper part of the medulla, and its fibres are 

 lost on either side in the lobes of the cerebellum. The pons varolii is 

 the forward boundary of the medulla oblongata, but the fibres which en- 

 ter into the structure of the medulla pass on and contribute to the forma- 

 tion of other organs. The anterior pyramids are entirely of fibrous 

 structure, and pass forward behind the pons varolii, some of the fibres 

 passing between those of the pons. Beyond the pons they continue in 

 a large diverging bundle on each side forward toward the cerebral lobes, 

 and above or anterior to the pons they are denominated the peduncles of 

 the brain, or the crura cerebri. The peduncles are not, however, made 

 up exclusively of the fibres from the anterior pyramids which are effer- 

 ent or motor, but on their posterior part there are afferent or sensory 

 fibres. These are, in part, derived from the posterior pyramids, and, in 

 part, from the restiform bodies. The posterior pyramids as they pass 

 forward diverge from each other, and at the same time approach the an- 

 terior pyramids, and thus form a layer of sensory fibres on the dorsal 

 side of the crura cerebri. In this movement they are likewise accom- 

 panied by a portion of the fibres from the restiform bodies. As the 

 posterior pyramids pass through the pons varolii, a portion of their fibres 

 decussate, crossing from each side to the other. 



FIG. 272. Side view of part of 

 the Brain of the Horse. 



1. Medulla Oblongata. 



2. Restiform body. 



3. Position of Olivary body. 



4. an terior pyramid. 



5. On the Pons Vavoln. 



6. Middle peduncle of the cere- 

 bellum, that part of the figure 

 above (6) is the cerebellum. 



7. Peduncle of the Cerebrum, 

 or crus cerebri. 



8. Testis, the rear biilb of the 

 Corpora Quadrigemina, or op- 

 tic lobes. [same. 



9. Natis, the front bulb of the 



10. Corpus geniculatum inter- 

 14. Sensory root of the fifth nerve, trigem- 

 15. Motor root of the same. [inum. 



16. Facial nerve, sevonth pair. 

 17. Auditory nerve, eighth pair. 



This sensory layer on the back of the crus cerebri, is called the tea- 

 mentum ( cover ). The anterior or motor portion is called the foot of 

 the crus. Beneath the corpora quadrigemina the gray matter of the 



num of the optic thalamus. [same. 



11. Corpus geniculatum externum of the 

 12. Optic nerve. [bandofReil. 



13. Fourth nerve, pathetic, resting on the 



