ABNORMAL GROWTH 129 



arm of 16 per cent., the hand of 7-1. 1 The length of the middle 

 ringer is actually decreased relative to normal. There is thus 

 not only a growth-gradient in the arm, but an indication that, 

 as in male stag-beetles (p. 115), the excessive tilting of one 

 end of the gradient above normal has led to a slight depression 

 of the other end below normal. The fact that the proportions 

 of the segments of the lower limb are not affected is interpreted 

 by Nanagas as meaning that the disturbance to growth occurred 

 very early, before the differentiation of the hind-limb had 

 begun. There appears, to be, further, a slight graded effect 

 upon the trunk. The arm circumference is 13-0 per cent., 

 the chest circumference at the nipples 7-5 per cent., at the 

 tenth rib 1-3 per cent, above normal. In any case, the corre- 

 lation of poor development of head with increased development 

 of the region next behind it is interesting. It may be inter- 

 preted as due primarily to the excess growth of the forelimb 

 region ; or more probably the primary factor is the failure 

 of the head to develop, which then, in accordance with the 

 views of Child and of Stockard, permits a higher development 

 of regions posterior to it in the body-gradient (Fig. 69, left). 

 A further teratological study which is also relevant to our 

 purpose is that of Mead (1930), based on a single monster of 

 34-8 cm. crown-heel length. When the measurements were 

 compared with those computed for a normal embryo of the 

 same crown-heel length, it was found that the head was very 

 much enlarged ; likewise the arms, in diameter more than in 

 length. The trunk was enlarged in breadth, more so anteriorly 

 than posteriorly ; its anterior portion was markedly reduced 

 in length, its posterior portion slightly increased. And the 

 hind-limbs were slightly increased in length, but considerably 

 reduced in diameter. (The proportions of the segments of 

 the limbs were not disturbed.) This can most simply be inter- 

 preted as due to (1) an abnormally high growth-centre anteri- 

 orly with growth-gradient extending backwards. But (2) this 

 is complicated by differences in growth-intensity in the different 

 planes of space. From the shoulder region posteriorly there 

 is an abnormal growth-gradient in the breadth-dimension, 

 above normal anteriorly, below normal posteriorly (cf . the arm 

 of Nanagas' specimen, supra) ; and growth in the length- 

 dimension is inversely correlated with growth in the breadth- 



1 This is the statement in Table I, and appears to be correct. On 

 p. 477, however, the value is given as i-i per cent., and on p. 485 

 as 2 per cent. ! 



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