716 General Etiology of the Diseases of the Peripheral Nerves. 



simply the result of the removal of a considerable quantity of 

 fat. Definite results can be obtained only by microscopic ex- 

 amination which reveals, in acute cases, dilatation of the ves- 

 sels, cellular infiltrations, small hemorrhages in many cases, 

 in chronic forms an increase in the amount of connective tissue, 

 and in both cases degeneration and disappearance of the nerve 

 fibers extending in the peripheral direction from the seat of 

 the disease. If the seat of the inflammation is on the central 

 side of the spinal ganglia or the ganglia of the cranial nerves, 

 the degeneration is found in the sensory roots of the spinal 

 or cerebral nerves and in the posterior columns of the cord 

 or in the sensory root of the trigeminal nerve. As a rule the 

 lesions do not involve the Avhole cross-section of the nerve trunk 

 to the same extent. 



If the inflammation starts in the connective tissue sur- 

 rounding the nerve it is known as perineuritis, but if it has its 

 starting point in the intraneural interstitium it is called in- 

 terstitial neuritis. The term parenchymatous neuritis is re- 

 served for those cases in which the primary lesion is a degen- 

 eration of the nerve filler. 



Diseases of the central nervous system and its membranes 



frequently cause paralysis and other functional disturl)ances 

 of the peripheral nerves, but, strictly speaking, these do not 

 belong to the diseases now under consideration. On practical 

 grounds it appears to be advisable, however, to refer to them 

 while the subject of the diseases of the peripheral nervous sys- 

 tem is under discussion. 



Diseases of this kind involving the purely motor nerves 

 abolish the conductivity of the affected nerves, either entirely or 

 in part, either through the entire cross-section of the nerve or 

 in a part only. This results in an infranuclear (peripheral) 

 paralysis of the muscles supplied by the nerves in question. 



In mixed nerves the conductivity is preserved for a time, 

 and not rarely till the time of death in the sensory nerve fibers 

 which are apparently more resistant, provided the nerve be not 

 completely severed or crushed. In view of the fact that the 

 sensory nerves are stimulated more easily by various influences, 

 disease of a portion of a mixed nerve, as a rule, leads to pain 

 through the whole lengih of the nerve and throughout the 

 area supplied by it. The contractions and spasms of ttie 

 muscles concerned and the exaggeration of the reflex irrita- 

 bility which is observed in rare cases are due to stimulation of 

 the sensory fibers. The reflexes persist so long as the conduc- 

 tivity of the motor nerves is not destroyed. As the motor 

 nerves which are very easily injured lose their conductivity 

 right from the start or very soon after, muscular spasms and 

 exaggeration of the tendon reflexes are very rarely observed 

 in diseases of the peripheral nerves, except in disease of the 

 membranes, in which the entirely different mode of development 



