SHOULDER GIRDLE AND ANTERIOR LIMB 505 
TABLE 2 
Showing the results following complete removal of the third, fourth, and fifth somites 
and the pronephros 
ee CONDITION OF THE GIRDLE AND THE EXTREMITY 
INDIVIDUAL eres 
iecey Supraseapula Scapula Procoracoid Coracoid Humerus 
1B. 1183.,..5el) 9 283 absent present present present present 
iBall anion || Pabsent present present present undifferen- 
tiated 
[Eb eee 26 | absent present present present absent 
1oy Ce eee 27 | dorsal half | present present present present 
absent 
The absence of the limb in case Ex 1 is no doubt due to the destruction of its 
rudiment in the removal of the pronephros. 
Lewis (op. cit.), however, in addition to demonstrating this same 
fact, showed that definite defects in the ventro-lateral muscu- 
lature follow the removal of the myotomes of the limb region. 
An examination of figure 8 will show that, in this case, there is 
complete absence of the ventro-lateral musculature on the oper- 
ated side. This is, however, not always the case, for in others in 
which these same myotomes were completely excised, the ventro- 
lateral musculature is partly filled in by a compensatory elonga- 
tion of the derivatives of intact myotomes. This same observa- 
tion was also made by Lewis. 
In the absence of the suprascapula, the m. dorsalis seapulae, 
which normally runs from the proximal end of the humerus over 
the external surface of the suprascapula (fig. 7, m.dsc), now 
attaches to the scapula (fig. 8). 
It is essential, in order to remove successfully the supra- 
scapula rudiment to include the pronephros. Its removal fa- 
cilitates cleaning of the wound and thus affects indirectly the 
results of the experiment even though it exerts no direct influ- 
ence. ‘This applies as well to removal of the limb bud as a whole 
(Harrison, ’15). 
Since removal of the outer portions of the third, fourth, and 
fifth somites suppresses development of the suprascapula and 
since there is no visible rudiment for this element at the time 
of the operation, the experiments show that the suprascapula is 
