ANATOMY OF A MONODACTYLOUS FOETUS 409 



had no power of extension. The probable exi)hination is that 

 there was a condition such as present in the case I have dis- 

 sected. The fact that in both these cases the flexors are evi- 

 dently better developed than the extensors is significant and 

 seems to point to certain definite conditions in the muscles 

 being associated with the deformity. 



MUSCLES OF THE HAND (figs. 7 and 8, L.) 



Only one muscle is present here. It is a lumbrical, arising in 

 the metacarpal region from the lateral side of the flexor digi- 

 torum profundus as this latter muscle passes into its tendon. 

 The lumbrical passes in a spiral direction distally and laterally 

 on to the dorsal surface of the digit where it inserts into the 

 dense fibrous tissue over the phalanges. 



NERVES OF THE LEFT ARM 



The whole brachial plexus was dissected out as shown in 

 figure 8 and conformed in all its arrangement and branches to 

 the typical formation. Therefore it is only necessary to describe 

 the course and distribution of its main terminal branches. 



From the 'posterior cord 



1. Axillary nerve. Normal course and distribution to skin, 

 deltoid and teres minor muscle, and to shoulder joint (figs. 8 and 

 10, A. N). 



2. Radial nerve. Runs ventral to the latissimus dorsi tendon, 

 then winds behind the humerus (figs. 8 and 10, R. N) in the 

 musculospiral groove, here giving branches to the three heads 

 of the triceps muscle, and then enters the space between the 

 triceps and postaxial portion of the brachialis muscle, where it 

 supplies this part of the brachialis and gives off the dorsal anti- 

 brachial cutaneous nerve. 



A short distance further on the nerve divides into 



a. The superficial radial (figs. 9 and 10, S. R. N) which runs a 



cutaneous course on the lateral side of the whole length of the 



forearm and hand. 



