ABNORMAL GROWTH 131 



also numerous cases scattered in the Nouvelle Iconogmphie de 

 la Salpetriere, and Stockard (1931) treats of the question in 

 a comprehensive way. In general, it appears that simple 

 pituitary gigantism is associated with relatively long limbs, 

 but within the limbs there is not much proportionate change, 

 or a slight defect in hand and foot. In acromegaly, however, 

 whether associated or not with gigantism, the relative sizes 

 of hand and foot are increased. 



In ateliotic dwarfs, the proportions of the limbs to the 

 trunk and of the limb-segments to each other are not affected. 

 In achondroplastic dwarfs, however, not only are the limbs 

 abnormally short, but the segments are differentially affected ; 

 the proximal segments are markedly reduced, the hand and 

 foot scarcely at all. (In mongoloid dwarfs, on the other hand, 

 relatively short fingers and toes are among the most striking 

 differential characters (Davenport and Swingle, 1927).) The 

 hind-limb is usually less abnormal than the fore-limb. In 

 breeds of dogs with markedly reduced limbs, which Stockard 

 (1. c, p. 228, etc.) compares with human achondroplasia, ascrib- 

 ing both to abnormalities in the thyroid, we get a similar 

 modification of the proportionate size of the limb-segments. 

 In the basset-hound he states that the hind-feet are dispro- 

 portionately enlarged, which would indicate a tilting of the 

 whole gradient so that the proximal region is below, the distal 

 region above the normal level (cf. pp. 89, 115). Unfortun- 

 ately he gives no precise details. 



The relatively large size of limbs in giants can only be due 

 to their increased heterogony during growth ; while achondro- 

 plastic types afford evidence of a disturbance in the growth- 

 gradient as well as the general growth-coefficient of the limbs. 

 From Stockard's work it is clear that, in dogs, the achondro- 

 plastic short type of limb may be inherited separately; it 

 depends upon a single Mendelian gene. 1 



1 The apparently genetic achondroplasia (chondrodystrophy) found 

 in fowls (Landauer, 1927) differs in its results from that of mammals 

 in various ways. In the first place it does not affect the fore-limb, 

 while the hind-limb and most other parts of the body are markedly 

 affected. Secondly, in the hind-limb the tibia is more affected than 

 the femur. In the pelvis, growth in length is little affected, but many 

 breadth-measurements are enlarged. In a dwarf six-months-old 

 chicken whose dwarfism was apparently of myxoedematous origin, 

 Landar (1929) comes to the conclusion that its deviations from normal 

 proportions (which were negligible in the wing, but marked in the leg, 

 skull and pelvis) can mainly be attributed to a suppression of the 

 later phases of growth. 



