131 



most posterior nerve to supply the nerves of the limb than when the 



XXVIII also contributes and that a still greater number of spinal 

 nerves is often utilized to supply the nerves of the limb when the 



XXIX spinal nerve contributes to the nerves of the limb. In other 

 words that an anterior or high position of the plexus, may be marked 

 also by a reduction in the number of the spinal nerves supplying the 

 nerves of the limb. Failure of distal spinal nerves to enter the nerves 

 of the limb is much more frequent and more marked than the entrance 

 of proximal spinal nerves into the nerves of the limb. 



Of the spinal nerves contributing to the anterior limb-nerves the 

 XXI nerve never sends a large branch of supply and the XXII seldom 

 does so. The main source of supply is from the XXIII nerve when 

 the XXIV nerve sends the greater number of its fibres to the posterior 

 nerves of the limb and from either the XXIII or XXIV when the 

 XXIV sends the bulk of its fibres to the anterior nerves of the limb. 



Of the spinal nerves contributing to the posterior nerves of the 

 limb the XXIV spinal nerve varies greatly in the number of fibres 

 that it contributes, the XXV and XXVI nerves always are large, the 

 XXVII nerve varies greatly in size, the XXVIII seldom, and XIX 

 nerve never contributes a large branch to the posterior nerves of 

 the limb. 



Few statistics relating to the anterior and posterior limits of the 

 lumbal-sacral plexus have been published. 



The distal spinal nerve to contribute to the sciatic nerve is 

 commonly stated to be most frequently the XXVIII spinal nerve (the 

 3. sacral). This accords with our findings. In 246 plexuses, the 28. 

 spinal nerve was the last to contribute such fibres in 185 instances 

 (75,2 7o)- The XXVII spinal nerve was the last to contribute fibres 

 to the tibial nerve in 25 instances (10,2 7o) and the XXIX spinal nerve 

 in 35 instances (14,2%). Paterson^) records the findings in twenty- 

 three plexuses. The distal limit to the plexus, if the small sciatic 

 be not included, he reported to be the 2. sacral nerve in 10 and the 

 3. in 9 instances. If the small sciatic be included the limits become : 

 sacral 2. five times, sacral 3. fourteen times, in plexuses the furcal 

 nerve of which was XXIV; and sacral 3. three times and sacral 2. 

 (= XXVIII Sp. N.) once in plexuses the furcal nerve of which was 

 XXV. Among these plexuses then, there was a far greater percentage 

 of those limited by the XXVII spinal nerve than in those examined 



1) Paterson, The Origin and Distribution of Nerves to the Lower 

 Limb. Journal of Anatomy and Physiology, 1894, p. 84 and 169. 



