SHOULDER GIRDLE AND ANTERIOR LIMB 507 
TABLE 3 
Showing the results following the removal of the area a-e X 1-8 (text fig. 1) including 
the outer portion of the somites, the pronephros, and the limb mesoderm 
CONDITION OF THE GIRDLE AND THE LIMB 
INDIVIDUAL AGE 7 = 
Suprascapula Scapula Procoracoid Coracoid Humerus 
& | 
days 
RRO neers 26 | absent absent present present absent 
1S, Pee 26 | absent absent present present absent 
late eae 26 | dorsal por- absent present present absent 
tion | 
present 
BONS. 28 | absent absent present present absent 
Bis $0): 28 | absent absent | present present absent 
IRAE Perak 26 | small nod- absent | present present absent 
ule of 
cartilage 
Incomplete absence of the suprascapula in cases R 1 and R 2 is apparently 
due to imperfect removal of the rudiment. 
coracoideus, a muscle which normally runs from the proximal 
end of the humerus to the external surface of the coracoid (fig. 
7, m.spc). 
4. Limb-bud extirpations. The effects of the removal of a 
typical limb dise on the girdle (text fig. 1) are in accord with 
those described by Harrison (18). In individual H 2 sectioned 
twenty-two days after the operation, only the suprascapula, a 
very small procoracoid, and the coracoid were present (fig. 10 
and table 4). In another, H 5, only the dorsal part of the 
suprascapula was present in addition to a fragmentary procor- 
acoid and the coracoid (fig. 27 and table 4). In these cases the 
pronephros was removed with the limb bud, and the incomplete- 
ness of the suprascapula in the second case is no doubt due to a 
partial destruction of its rudiment in the removal of the pro- 
nephros. 
Since no limbs developed in experiment 3 after the removal of 
the area a-e X 1-5, it is obvious that the ventral portion of a 
typical limb dise (Harrison, 715 and ’18) which is shown in 
text figure 1 contains only girdle-forming cells. 
The formation of only a portion of the ventral zone of the 
