6 3 4 



NERVE-DEGENERATION AND NERVE-REGENERATION. 



improved by restorative remedies. Only the ignorant, misled by the signs of 

 increased irritability of the nervous system, would employ depressing measures. 

 In case of total obstruction of the blood-supply to the nerve-trunk, its irritability 

 may persist for from five to ten hours. 



If the terminal nerve-apparatus is exposed to a temporary disturbance of its 



B 



FIG. 223. Degeneration and Regeneration of Nerves: A, Early, 

 gross breaking up of the myelin. B, Further breaking up of 

 the myelin (osmic-acid stain). C, Disintegration of the axis- 

 cylinder, surrounded by (bright) fragments of myelin. D. 

 Accumulation of nuclei with remains of myelin (bright) in 

 the swollen spindle-shaped fiber. E, The new fiber passing in 

 a tortuous course through the old sheath. F, The new com- 

 pleted fiber, with the new sheath of Schwann (s) within the 

 old sheath of Schwann (sa) (after Cossy and Dejerine). 



normal nutrition, it responds to the restoration of normal nutritive processes by 

 the development of a more or less intense irritative process. The effective dis- 

 turbance of nutrition need exist a shorter time the more sensitive the nervous 

 end-apparatus in question is to the nutritive disturbance, such as cutting off of 

 the arterial blood-supply or interference with respiration. 



Long-continued excessive irritation of a nerve without suitable in- 

 tervals of rest for purposes of recuperation soon causes fatigue of the nerve 



