SCIATICA. 339 



ETIOLOGY. The nerves forming the sciatic plexus may be pressed 

 upon by carious or carcinomatous vertebrae, just where they pass through 

 the intervertebral foramen, and may thus be morbidly excited. And 

 sciatica not unfrequently depends on pressure, which acts on the sci- 

 atic plexus in the pelvis. In a patient with lymphatic leuchaemia, 

 whom I had the opportunity of observing at Greifswald, a severe in- 

 termitterit neuralgia, which was undoubtedly caused by the pressure 

 of the immensely-swollen retroperitoneal glands on the sciatic plexus, 

 was for years the most prominent symptom. Tumors in the pelvis 

 occasionally act in the same way, by pressure on the sciatic plexus, 

 particularly ovarian cysts, collections of hard faeces, or, as in a very 

 instructive case of Bamberger's, collections of cherry-pits in the sig- 

 moid flexure, also the gravid uterus, particularly if the child's head 

 remain long impacted. Cases of sciatica that are very obstinate, but 

 usually terminate in cure, result from the pressure of exudations of 

 parametritis and perimetritis in the subperitoneal tissue or in capsu- 

 lated intraperitoneal spaces on the sciatic nerve. 



Lastly, irritation of the peripheral branches of the sciatic may 

 sometimes be found as a cause of the sciatica. In this class belong 

 the cases due to pressure from tight boots, from phlebotomy, an- 

 eurisms of the arteries of the lower extremity, tumors near the nerve, 

 etc. 



Among the causes of sciatica that leave no perceptible anatomical 

 changes are excessive straining, suppression of habitual perspiration 

 and exanthemata, and catching cold. It is quite natural that the lat- 

 ter should occur. Indeed, the majority of cases of sciatica are of rheu- 

 matic origin, as they result from exposure to cold of the skin covering 

 the sciatic nerve, as occurs particularly in windy privies. It is not at 

 all astonishing that, among the cutaneous nerves, the trigeminus and 

 sciatic should be affected most frequently ; the former being all day 

 exposed to the danger of catching cold, and the latter being exposed 

 for a short time once or twice daily. 



Statistics show that sciatica is one of the most frequent forms of 

 neuralgia, that it rarely occurs among children, is most frequent be- 

 tween the ages of twenty and sixty years, and that it occurs more fre- 

 quently in males and the lower classes than in females and the higher 

 3lasses. 



SYMPTOMS AND COURSE. Most cases of sciatica support Horn- 

 berg's assertion that there is no cutaneous nerve of the lumbar and 

 sacral plexus, from the hip-joint to the ends of the toes, which may 

 not be affected with neuralgia, and that it is only tradition that locates 

 the pain in the trunk of the nerve. The most frequent seats of the 

 neuralgic pain are the nervus cutaneus femoris posterior, in which 



