Differentiation of Neuroblasts 33 
It was killed, sectioned, and stained as given above, and the oper- 
ated and unoperated sides carefully compared. 
The bones and muscles were well defined and easily identified 
and the course of the nerves traced without difficulty. Fig. 3 shows 
the location of the chief wing muscles and Fig. 33, 4, the periph- 
eral distribution of the brachial plexus on the normal side. Since 
the branches of the 14th, 15th and 16th nerves which innervate 
the vertebral musculature are not affected, these muscles being 
quite intact, and the branches arising from the separate trunks 
before the formation of the brachial plexus, their distribution has 
been neglected. 
On the operated side the bones of the shoulder girdle are present 
but defective; the clavicle and scapula are, however, only slightly 
abnormal. Of the muscles the trapezius, rhomboideus, and sub- 
clavius are not noticeably affected; the pectoralis major, pectoralis 
secundus, coraco-brachialis, latissimus dorsi, teres et infraspinatus 
and subscapularis are present but defective, while the deltoides sup- 
raspinatus, biceps, pectoralis tertius, coraco-humeralis, scapulo- 
humeralis, and triceps are entirely wanting. Fig. 33, B, shows the 
peripheral distribution of the brachial plexus on this side. It will 
be seen by comparing this with 4 that wherever a muscle 1s 
missing the corresponding nerve 1s also missing; otherwise the 
distribution is the same as that of the opposite side. 
As A and B are drawn on the same scale they show some- 
thing of the quantitative loss, but measurements give this more 
exactly. It is difficult to arrive at the exact dimensions of the 
nerve trunks from sections without making reconstructions, but as 
a means of comparison each of the three nerves involved was 
measured directly below the union of the ventral root with the 
ganglionic root, and the number of sections in which each appears 
at this place counted. 
From the data thus obtained the following percentages of loss for 
the nerve trunks were calculated : 
WIDTH THICKNESS 
PERCENT PERCENT 
MALUITIEGVEH OP AA caste terstcitieit sve oie.tiple aloo siete els vletepucieie’s fiels rie? “erin aer 34.1 25 
RIG ELLE GV ets tet taaiaN-Nal e/a olafo\a/ola)e.viz)rie/siai=)e\psle(ei= iniciafeta/elsiefelole = ce afela-tevo(eltnfet= 17.6 36.3 
MALEMTACEN Crepe eerste TaicT oie) Se, os Sissel «cen ale ola ote avclinis ekeinnyelere a lannkelsveuctenimeel sya 35-8 30 
