Bardeen, Variations in tJic Lumbal' Plexus. 201 



number of plexuses indicated by the numerals. The numbers 

 are placed under Roman numerals representing the spinal 

 nerves which give rise to direct branches to the peripheral nerves 

 in question. The "c" represents a branch of communication 

 between two spinal nerves. Thus -^^ '^^^ indicates that the 

 ileo-hypogastric arose in one case from the twelfth thoracic nerve 

 when there was a proximal branch connecting the eleventh 

 with the twelfth thoracic nerve. The percentage at the bottom 

 of some of the columns indicates the ratio between the number 

 of plexuses in which the given spinal nerve is distributed to the 

 peripheral nerve in question and the total number of plexuses 

 examined. In making the percentages it is not assumed that 

 a given spinal nerve sends fibers more than one segment below 

 through the communicating branches. 



There is little need of an extended review of the conditions 

 tabulated. The nature and variety of the relations of the nerves 

 leaving the plexus to the spinal nerves forming it is shown in 

 the tables. 



Eisler, Paterson, and others who have examined the lum- 

 bo-sacral plexus in man and other animals have pointed out that 

 the plexus as a whole may vary considerably in relation to the 

 spinal nerves composing it. It may present a very high form 

 in which a given spinal nerve plays the role usually played by 

 the one just below or a very low form in which the reverse is 

 true. The plexus may vary anywhere between these two ex- 

 tremes. They have also mentioned that the various parts of 

 the plexus may vary as well as the plexus as a whole. Not 

 enough stress has been put upon this latter point however. 

 Thus for instance one might expect, from the association of the 

 eleventh thoracic with the plexus, the existence of a general 

 "high" form, yet this was the case to a m.arked degree in 

 none of the six plexuses into which the eleventh nerve en- 

 tered. The entrance of the fifth nerve into the lumbar plexus 

 likewise was associated with a general marked low form in 

 but two of the eight bodies in which the condition was found. 



