BRACHIAL PLEXUS OF NERVES IN MAN 303 



In the different nerves of the same plexus, there is also some 

 variation in the amount of fat in the epineurium and of the 

 amount of connective tissue forming the epineurium. The 

 amount of moisture is of less moment though without care it 

 might easily happen that the moisture in the different nerves 

 would be unequal. 



It is also extremely difficult to be sure that one is getting correct 

 measurements. Very slight pressure against the muscle dorsal 

 to the nerves such as is caused by traction on the limb or permit- 

 ting it to drop dorsally will cause a very appreciable amount of 

 flattening. In the comparisons given above, I have endeavored 

 to be very careful to eliminate this source of error so far as possible 

 and have verified each measurement several times, but still do 

 not feel confident of the results. It is, of course, easy to see on 

 inspection that all of the nerves in a plexus are not of the same 

 size, some of them are usually markedly larger or smaller than 

 the others. On the other hand, I feel quite sure that the differ- 

 ences between certain of the nerves especially in the center of 

 the plexus are in many cases so small that under slightly altered 

 conditions two different observers might obtain quite opposite 

 results. Taking all these things into consideration, I feel that 

 the method of classifying plexuses as prefixed and postfixed, 

 based upon the size of the nerves, as we are able to determine 

 them, is of very doubtful value, and that for the human plexus 

 it should have Httle or no weight as an accessory to other 

 methods. 



ARRANGEMENT OF NERVE BUNDLES IN A NERVE 



As is well known, each of the anterior rami of a spinal nerve as 

 it passes out between the muscles is composed of a large number of 

 nerve fibers collected into bundles, funiculi. Each funiculus is 

 surrounded by a more or less definite connective tissue sheath, 

 perineurium. These bundles are bound together by more con- 

 nective tissue epineurium, which also finally forms a sheath 

 around the whole nerve. 



The funiculi in a nerve do not run along parallel with one 

 another but they interlace and divide frequently and the branches 



