172 



INITIATIVE IN EVOLUTION 



their humble way : they may be even dignified with the name 

 " character." 



They are often double over the joints of the fingers and toes, 

 but, from the functional point of view and for simplicity, may be 

 reckoned as single. 



Chief Types. 



The most common types of them in the hand of man are 

 shown in the example given in Fig. 71. 



Fig. 72. — Foot of com- 

 mon squirrel. 



Fig. 73. — Flexures on foot of 

 vulpine phalanger. 



1. A flexure over each phalangeal joint. 



2. A flexure at the bases of the digits. 



3. A flexure over the metacarpophalangeal joints of D 2, 3, 4 

 and 5 with an oblique direction, called linea mensalis. 



4. A flexure over these same joints and oblique in direction, 

 but nearer to the wrist — the linea cephalica. These 

 flexures. 3 and 4, though arising from the flexion of one 

 set of joints should be looked at as separate folds because 

 of their time-honoured popular names. 



