ANATOMY OF A MONODACTYLOUS FOETUS 419 



I could not secure the journal containing his original article but 

 Ballantyne ('04) in his text l^ook and Schenk ('07) in an article 

 on a case of defect of the ulna agree in their accounts of Kiim- 

 mel's cases which can be taken as correct. He found SO in- 

 stances of defect in the bones of the forearm of which 67 were 

 of the radius, 13 of the ulna. In the case of the ulna it was 

 defective in 5, totally absent in 8 instances. In some of these 

 cases there was associated absence of the ulnar side of the carpus 

 and one or more fingers on the ulnar side of the hand. 



The muscles of the limb definitely appear first proximally and 

 differentiation proceeds distally. It might be expected that the 

 muscles of the shoulder girdle and upper arm, being the first to 

 appear after the skeletal deformities were produced, might show 

 some anomalies. They do exhibit anomalies, but peculiarly 

 not anomalies of defect, but of excess, such as supernumary 

 heads and increased insertions. Of course, in the forearm and 

 hand grave defects are associated with the loss of the skeletal 

 structures. 



The question naturally arises as to whether the muscle 

 anomalies are a consequence of the skeletal defects or were inde- 

 pendently produced by the same vice of development or nutri- 

 tion to \\^hich the absence of the bones is due. In this connec- 

 tion it is to be noted that the suppression of muscles in the fore- 

 arm is not confined to the ulnar border of the arm but affects 

 also the radial side, so that more than mere absence of the skele- 

 ton underlies the anomalies. This can be proved by the fact 

 that muscle is independent and self-differentiating. Muscles 

 develop independently of functional activity as shown here by 

 the two humeral heads of the triceps, inserted also on the hu- 

 merus, incapable of movement, yet well developed. Harrison 

 ('04) also proved that muscles develop independently of the 

 nervous system, for he removed the spinal cord in early frog 

 embryos, before the muscles had differentiated or received any 

 nervous connection and yet the normal process of muscle de- 

 velopment and grouping occurred. This power of self-differ- 

 entiation goes right back to the ovum where Conklin ('05) has 



