THE NERVOUS SYSTEM 



cerebral nerves or to the anterior gray columns of the spinal cord; whence the 

 lower motor neurons, also known as primary motor neurons, relay the impulses 

 to the muscles. It is possible that another and much shorter element is inter- 

 calated between the two chief units of this conduction system. 



The motor cortex occupies the rostral lip of the central sulcus and the ad- 

 jacent portion of the anterior central gyrus, extending over the dorsal border of 



Motor cortex 



...Posterior limb of internal capsule 



. Genu of corpus cattosum 



Basis pedunculi of mesencephalon 



----^Longitudinal fascicles of pons 



Pyramid of medulla ablongata 



Lateral corticospinal tract 

 Ventral corticospinal tract 



Fig. 237. The corticospinal path. 



the hemisphere into the paracentral lobule. Within this area the skeletal mus- 

 culature is represented hi inverted order, that moving the toes near the dorsal 

 border of the hemisphere. The area from which the corticobulbar tract arises 

 is only a small part of the whole, and is situated near the lateral cerebral fissure 

 (the region marked Eyelids, Cheeks, Jaws, Lips in Fig. 236). From all the rest 

 of the motor cortex arise the fibers of the corticospinal tract. 



