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nerve contributed slightly to the formation of the tibial nerve. In 

 three instances the XXI spinal nerve sent a small branch of com- 

 munication to the XXII spinal nerve. Most of these fibres seemed to 

 enter the lateral cutaneous nerve. In all instances the XXII to the 

 XXIV spinal nerves contributed to the formation of the femoral and 

 obturator nerves, the XXIV contributing the great bulk of the fibres. 

 The branch of communication from the XXIV to the XXV spinal 

 nerve was in all instances small. In two instances out of ten, the 

 XXVIII spinal nerve contributed a branch to the peroneal nerve. 



Under type G, we have 20 plexuses in which the XXV was a 

 furcal nerve and in which the XXII to the XXIX spinal nerves 

 contributed to the nerves of the limb. In 11 instances the XXV nerve 

 contributed to the formation of the obturator nerve, in 20 instances 

 to the formation of the femoral. In 8 instances the XXIV spinal 

 nerve contributed to the sacral plexus. In 4 out of the 10 instances 

 observed during the years 1898 — 1900 the XXVIII spinal nerve contri- 

 buted to the formation of the peroneal nerve. 



The Accessory Obturator Nerve. 



The accessory obturator nerve was found in 20 (8,5%) of the 

 246 plexuses studied. This brings it into accord with the findings 

 of most investigators who have studied the subject. As quoted in 

 Eisler's article, Schmidt found it in 8 — 9 instances in 70 plexuses; 

 PoKORNY 3 times in 40 plexuses; and Krause estimated it at 10%. 

 EiSLER himself found it in 35 out of 120 plexuses (29%). This is 

 difficult to explain. Special notice is given to this nerve in the recent 

 editions of the standard text books on anatomy. Our students were 

 on the lookout for it. It is exceedingly improbable that in any great 

 number of instances it would have escaped attention had it been 

 present. Eisler's work seems to have been careful. We must assume 

 that he encountered a very unusual run of plexuses with an accessory 

 obturator nerve. 



This nerve was found twice in the 25 instances of type B plexus, 

 eight times in the 63 instances of type C plexus, eight times in the 

 104 instances of type D plexus and once each in the 15 instances of 

 type F and the 20 instances of type G plexus. It is therefore apparently 

 most common in those plexuses which have a position slightly more 

 anterior than the usual position. It arose 9 times from the XXIII 

 spinal nerve, 3 times from the XXIV and 8 times from the XXIII 

 and XXIV. 



