EFFERENT PATHS AND REFLEX ARCS 



325 



"the basal forebrain bundle" of Edinger (1887), which is represented in mammals by the 

 striofugal fibers of the ansa lenticularis. It is clear that this fascicle, which persists through- 

 out the vertebrate series, must subserve important functions; and it is probable that it 

 forms a part of the extrapyramidal motor path. 



THE CORTICO-PONTO-CEREBELLAR PATH 



The cortico-ponto-cerebellar path is an important descending conduction 

 system which places the cerebellum under the influence of the cerebral cortex. 

 Since a part of the corticopontine fibers are collaterals given off to the nuclei 

 of the pons by the corticospinal fibers, and since in many mammals practically 



Red nucleus 



\Purkinje cell 

 i Cerebellum 



Frontopontine tract 



Corticospinal tract 



Nuclei pontis 



Muscle 

 Spinal cord 



- Dentate nucleus 



~ Brachium conjunctivum 



" * Brachium pontis 

 Rubrospinal tract 



Corticospinal tract 



Fig. 242. The cortico-ponto-cerebellar and cerebello-rubro-spinal paths. (Modified from Cajal.) 



all of the corticopontine fibers are represented by such collaterals (Cajal, 1909), 

 one can scarcely avoid the conclusion that through this system the coordinating 

 and tonic mechanism of the cerebellum is brought into play for the regulation 

 of movements initiated from the cerebral cortex. In this sense the idea of 

 Cajal (1911) that there exists an indirect motor path to the spinal cord through 

 the cerebellum is probably correct (Fig. 242). 



Neuron I. From pyramidal cells in the frontal lobe of the cerebral cortex 

 fibers pass through the anterior limb of the internal capsule and the medial one- 



