PHYSIOLOGY OF THE POSTERIOR PITUITARY. 501 



come from every part of the underlying structures and only 

 reach the cerebral elements through paths that are continuous 

 with the capsule's tissues. Again, the organ's vessels penetrate 

 it by way of the infundibulum; the vasomotor supply of these 

 vessels requires protection from the powerful stream of im- 

 pulses to which the organ's intrinsic structures give rise. That 

 a profuse padding of cellular tissue is Nature's resource under 

 such conditions is well illustrated by the following remark of 

 Dejerine's: "The vessels of the central nervous system are 

 surrounded by two sheaths of a different kind: the internal 

 is connective in nature and belongs to the mesodermic layer; 

 the external, neurogliar in nature, is developed at the expense 

 of the external, or ectodermic, layer." 



Berkley, referring to the various cellular structures in the 

 deeper portion of the lobe supplied with long extensions, says: 

 "The axis-cylinder extensions of all the cells in the inferior 

 portion of the lobe turn upward. . . . Those belonging 

 to the larger proportion of the smaller cells of the superior 

 border turn upward and intermingle with the marginal fiber 

 net-work. . . . All the axis-cylinder processes and the 

 long dendrites have a general tendency upward and forward, 

 both dendrites and neuraxons branching as they proceed on- 

 ward: but all traces of the dendrites of the inferior and median 

 cells of the lobe are lost some little distance below the superior 

 edge, and then the neurons only are intermingled with the 

 extensions of the smaller superficial cells, passing them, how- 

 ever, before the border is finally reached, where they spread 

 out into a most extensive fret-work of fine varicose fibers, still 

 retaining something of their previous longitudinal arrange- 

 ment from the threads of the uptending fibers being coarser 

 than the lateral and intermingling branches. It is doubtful 

 whether any of these fibers pass beyond the limit of the lobe 

 into the infundibulum; our sections give no evidence of such 

 an arrangement." This upward tendency of all cells, and the 

 evident concentration of their functional activity at the upper 

 extremity, seem to us to further emphasize the identity of the 

 posterior lobe as a powerful source of energy. Its junction 

 with the end of the infundibulum becomes, under these cir- 

 cumstances, the normal pathway for all the energy that the 



