GENERAL PHYSIOLOGY. 



33 



if anatomy places the upper bounds of the spinal cord at the 

 point of the occipito-atloidean articulation, the physiologist 

 extends the spinal cord to the interior of the cranium, as well 

 as along the vertebral canal, and even as far as the sella 

 turcica, where it ends with 

 the pituitary body (bulb, 

 protuberance, cerebral pe- 

 duncles, gray matter of the 

 third ventricle.) (Fig. 12.) 

 In the encephalic mass, 

 properly so called, the nerve 

 globules are distributed in 

 isolated layers, and form a 

 number of islets. These 

 masses are placed above 

 the cephalic extremity of 

 the spinal cord, and form in 

 this place series of trans- 

 verse bands. Near the 

 place where the spinal 

 cord bends before termi- 

 nating in the sella turcica 

 are found a number of 

 isolated little groups of 

 globular matter. They 

 form, in a manner, sepa- 

 rated stages in the cranial 

 cavity, and are placed in 

 concentric layers one upon 

 the other. (Fig. 12, D.) 

 These stages have received 

 different names ; the most 

 superficial of them is in con- 

 tact with the skull, and 

 appears in the form of an 

 undulating surface envel- 

 oping the whole, and is called the cortical substance of the 

 encephalon. (Gray substance of the cerebral convolutions. 

 Fig. 12, E, E.) Between this and the encephalic prolonga- 

 tion of the spinal cord (A) are found : two important groups 



* A, A, A, Spinal cord, with its commissures. B, Region of the protuber- 

 ance. C, Cerebellum. D, Thalami optici and corpora striata. E,E, Gray 

 matter (cortical substance) of the cerebral convolutions, a, a, a, Anterior roots. 

 P,P,P, Posterior roots. 



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Fig. 12. 

 Plan of the central nervous system. 



