596 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



general source of energy for the whole bed of cranial nerves, 

 irrespective of the individuality and purpose of each nerve, it 

 would have been similar in general construction to its mate, 

 the anterior lobe. That it is not distinctly suggests that each 

 group of neurons in the posterior pituitary lody is a highly 

 specialized center for a single class of nerves. Indeed, this is 

 experimentally, though indirectly, sustained by Andriezen's 

 researches. He could not have traced a direct nervous con- 

 nection with the olfactory bulb and with the cerebro-spinal 

 axis had the organ been a center for the production of energy 

 intended to be diffused promiscuously in the central gray 

 matter. 



Again, the connection between the posterior lobe and the 

 nervous system cannot be limited to the cranial nerves, since 

 we have seen how intimate is the functional relationship in 

 which afferent impulses obtain, between the middle brain and 

 the entire motor system. Were the cranial nerves alone in- 

 volved, the skeletal muscles would have to be omitted from 

 the list of structures under the organ's control. As we have 

 seen, removal of the middle brain abolishes all "bodily move- 

 ments," as Foster puts it, "carried out by means of co-ordinate 

 motor impulses, influenced, arranged, and governed by coin- 

 cident sensory or afferent impulses." 



Yet, how can the posterior lobe influence organs with 

 which it has no anatomical connection? Thus, the most prom- 

 inent motor paths, the pyramidal tracts, arise, in the cortex, 

 from the upper two-thirds of the central convolutions, pass 

 down behind the knee of the internal capsule, and then pene- 

 trate the middle third of the pes cerebri, then the pons and 

 the medulla, and finally pass down the cord. Where is the con- 

 nection with the posterior pituitary? When the tracts "emerge 

 from the pons," says Edinger, 62 "their fibers form two large bun- 

 dles in the ventral portion of the medulla," i.e., in the regions 

 of the middle brain, where, as we have seen, not only all nerves 

 endowed entirely or in part with motor properties the second, 

 third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, elev- 

 enth, and twelfth pairs are represented either by their nuclei 



e 2 Edinger: Loc. cit. 





