pedal locomotion ; while other muscles {e.g., tl 

 the forearm and fingers) revert to a former simpler arrange- 

 ment when the hand was mainly a grasping organ, and the 

 thumb was not opposable. 



As in the skeleton, we find that muscular anomalies include, 

 1, paleogenetic reversions, or complete restorations of lost 

 muscles; 2, neogenetic reversions, or revivals of former types 

 in the relations of existing muscles ; 3, progressive variations, 

 which either by degeneration or specialization point to future 

 types; 4, fortuitous variations, which cannot be referred to 

 either of the above. 



Duval observes that the flexor longus pollicis repeats in 

 reversion all the stages of its evolution between man and the 

 apes, in which it is a division of the flexor profundus. Gruber 

 and others have even observed the absence of the thumb 

 tendon. This is true of all the new muscles. Of this Testut 

 writes : " Ne dirait-on pas, en le voyant s'eloigner si souvent 

 de son etat normal, que la nature voudrait le ramener a sa 

 disposition primitive, luttant ainsi sans cesse contre l'adapta- 

 tion, et ne lui abandonnant qu' a regret l'une de ses plus 

 belles conquetes." 



Speaking of the hand, Baker 1 says : " On comparing the 

 human hand with that of the anthropoids, it may be seen that 

 this efficiency is produced in two ways— first, increasing the 

 mobility and variety of action of the thumb and fingers; 

 . second, reducing the muscles used mainly to assist prolonged 

 grasp, they being no longer necessary to an organ for delicate 

 work requiring constant readjustment." You have noticed 

 the recent discovery that the grasping power of infants is so 

 great that the reflex contraction of the fingers upon a slender 

 cross bar sustains their weight ; this power and the decided 

 inward rotation of the sole of the foot and mobility of the toes 

 are persistent adaptations. Our grasping muscle, the p: Jmari- 

 longus, is highly variable and often absent ; like the plantaris 

 of the calf, it has been replaced by other muscles, and its 

 insertion has been withdrawn from the metapodium to the 

 palmar fascia. In negroes we frequently find the palmaris 



K)p. cit., P . 299. 



