211 



ferred the terms "proximal" and "distal", the proximal types of plexuses 

 being those formed of the more anterior, the distal those of the more 

 posterior spinal nerves. 



According to the relation of the nerves of the limb to the spinal 

 nerves, the plexuses studied have been arranged in seven groups, 

 lettered A to G, pictured in figures 2 to 8, and tabulated in tables 2 

 to 8. 



I. Proximal or anterior origin of the nerves of the 

 limb. 



Plexus types A to C are those in which more anterior nerves 

 than usual enter into the formation of the main nerves of the limb. 



In type "A", see fig. 2 and table 2, we have the most anteriorly 

 situated plexus which we have encountered. As will readily be seen 

 from the table and from the picture, the XXI to the XXVI spinal 

 (1. lumbar to 1. sacral) nerves are those which enter into the 

 formation of the main nerves of the limb. This was found in a male 

 negro on the left side. On the opposite side of the body a plexus 

 of "type B" was found. The skeleton had twelve thoracic, four lumbar 

 six sacral and three coccygeal vertebrae. 



Under type "B", see fig. 3 and table 3, are classified 25 (about 

 10 7o) of the plexuses. Here the XXI, or XXH, to the XXVII spinal 

 nerves serve to furnish the main nerve supply of the limb. 



In 20 of the 25 plexuses (80 7o) the XXI spinal nerve contributed 

 to the lateral cutaneous nerve; in 15 instances (60 7o) it contributed 

 to the femoral and obturator nerves. In 20 instances the main bulk 

 of the XXIV spinal nerve was given to the sacral plexus; in 5 the 

 larger portion of the XXIV spinal nerve was given to the femoral 

 and obturator nerves. 



In all cases the XXIII spinal nerve was the largest nerve entering 

 the lumbar plexus. In one instance the XXIII spinal nerve sent a 

 few fibres into the branch of communication that extends from the 

 XXIV nerve to the sacral plexus. In seven instances the XXVII nerve 

 contributed a slight branch to the peroneal nerve, in seven instances 

 the XXVI spinal nerve was the last to contribute to this nerve. In 

 all instances the branch from the XXVII spinal nerve to the tibial 

 nerve was comparatively small, the main bulk of the fibres coming 

 from the XXV and XXVI spinal nerves. 



Under type "C", table 4, fig. 4, we have included 63 plexuses in 

 which the XXVIII spinal nerve also served to supply the nerves of 

 the limb. This type of distribution is somewhat similar to that 

 described under type D, except that the proportional distribution of 



14* 



