538 THE POSTERIOR PITUITARY AND THE NERVOUS SYSTEM. 



the substances soluble in ether are relatively increased owing, 

 in part, to fatty degeneration of the axis-cylinder," and that 

 "the percentage of phosphorus is markedly diminished (Mott 

 and Barratt)." 



Another process which seems to acquire a certain degree 

 of light is nerve-regeneration. It is obvious that if we grant 

 the axis-cylinder, as the extension of the axon, all functional 

 and nutritive attributes, we may easily explain peripheral 

 nerve-degeneration, but not regeneration, the peripheral seg- 

 ment being unprovided for by reason of the section. We know, 

 on the contrary, that a piece of the nerve must be removed in 

 order to prevent reunion, and that otherwise in two or three 

 weeks, and often earlier, its functions will be restored. New 

 cylinders and fibrils grow, acquire myelin, and, perhaps, guided 

 and assisted by (nucleated) neurilemma, soon meet those of 

 the peripheral segment and become connected with them. 

 Physiological functions of a normal kind must underlie this 

 process even in the peripheral end of the nerve; otherwise 

 union would not take place. Finally (we can only refer to a 

 few of the more prominent processes involved in the vast sub- 

 ject now claiming our attention) the functional phenomena 

 that follow after division of the cord distinctly indicate the 

 continuation of nutrition and the functional activity though 

 impaired in the distal fragment. Foster, for instance, says: 

 "In the mammal (dog) after division of the spinal cord in the 

 dorsal region regular and apparently spontaneous movements 

 may be observed in the parts governed by the lumbar cord. 

 When the animal has thoroughly recovered from the operation 

 the hind-limbs rarely remain quiet for a long period of time; 

 they move restlessly in various ways; and, when the animal 

 is suspended by the upper part of the body, the pendent hind- 

 limbs are continually being drawn up and let down again with 

 a monotonous rhythmic regularity suggestive of automatic 

 rhythmic discharges from the central mechanisms of the cord. 

 In the newly-born mammal, too, after removal of the brain 

 movements apparently spontaneous in nature are frequently 

 observed. But all these movements, even when most highly 

 developed, are very different from the movements, irregular 

 and variable in their occurrence, though orderly and purposeful 



