268 ANNALS NEW YORK ACADEMY OF SCIENCES 



Inteoduction 



The movements and locomotive mechanisms of animals were the 

 subject of a classic work by Borelli in 1680, entitled "De Motu Ani- 

 malium . . ." The chief pioneers of modern research were the brothers 

 Weber (Eduard and Wilhelm), authors of "Die Mechanik der mensch- 

 lichen Gehwerkzeuge," Gottingen, 1836. Marey, the author of the hand- 

 book on "Animal Mechanism" 1 (1874), invented elaborate apparatus for 

 analyzing and graphically recording the movements of the limbs of men 

 and animals, while more recently the mathematics of human locomotion 

 have been developed by 0. Fischer and others. General reviews of animal 

 mechanics and of human locomotion are given by Marey, 2 Haycraft 3 and 

 Luciani. 4 A very able analysis of the mechanism of locomotion in the 

 horse is given in "The Horse in Motion," by J. D. Stillman, 5 while the 

 extensive series of photographs by Muybridge 6 record the actual positions 

 of the limbs and body assumed in motion by ungulates and other animals. 



None of the above mentioned works considers the subject from the evo- 

 lutionary point of view. Eyder, 7 and especially Cope, 8 pointed out cer- 

 tain adaptations in the feet of ungulates, such as the reduction of the 

 ■digits in the "Diplarthra" and the so-called displacement of the metacar- 

 pals, and Cope used these observations in his argument for the hypothesis 

 of the transmission of acquired characters. He also made the following 

 very important observations : 9 



"In animals which leap, the distal segments of the limbs are elongated; in 

 those which do not leap, but which merely run or walk, it is the proximal seg- 

 ments of the limbs which are elongated. 



"Animals which run by leaping are divided into those which run and leap 

 with all fours, as Diplarthra, and those which run and leap with the posterior 

 limbs only, as the jerboas and kangaroos. In both types, the distal segments 

 of the hind limbs are elongated, and in the Diplarthra, those of the fore limb 

 also. 



"Animals which do not leap in progression (elephants, Quadrumana, bears) 

 are always plantigrade and have very short feet but elongate thighs and 

 mostly tibias." 



1 12mo. London, 1874. 

 a Op. cit. 



8 E. A. SchAfbe : Text book of Physiology. Edinburgh, and London, pp. 228-273, 

 1900. 



4 Physiologie des Menschen . . . Ins Deutsche tibertragen and bearbeitet von Dr. 

 Silvestro Baglioni und Dr. Hans Winterstein . . . Siebente Lieferung. Jena, 1906. 



5 Executed and published under the auspices of Leland Stanford, 4to, Boston, 1882. 



6 Animals in Motion . . . Third Impression 4to, London, 1907. 



7 Am. Nat., vol. 11, p. 607. 1877. 



8 "The Mechanical Causes of the Development of the Hard Parts of the Mammalia." 

 Journ. of Morphology, vol. 3, pp. 137-290. 1889. 



»IMd., p. 151. 



