252 GENERAL PHYSIOLOGY 



contractile side contracts from the cell-body outward, and thereby 

 the opposite side is extended; in the phase of expansion the 

 latter, by its elasticity, brings the cilium back into the position of 

 rest. According to the relative positions of the contractile and 

 the passively extended substances there results a movement in a 

 plane or a more complicated form. 



The work performed in ciliary movement is much less than 

 that of muscular movement. Engelmann, Bowditch and others 

 have calculated the work of ciliated epithelia, and recently Jensen 

 {'93, 2) has measured the force of a single ciliate-infusorian cell, 

 Paramcecium, which is well fitted for a great variety of investiga- 

 tions. Jensen determined that a Paramcecium, which possesses a 

 length of about 0'25 mm., is able to raise a weight of 0*00158 mgr., 

 i.e., about nine times the weight of its own body. 



The view is sometimes expressed that amoeboid movement has 

 nothing in common with muscular movement, and the latter 

 nothing in common with ciliary movement, that the three are 

 utterly different in kind. The above brief examination is sufficient 

 to show, however, that these three forms of contraction constitute 

 a, single group in contrast to all other modes of motion. It is true 

 that they show among themselves certain differences, and that at 

 first sight they appear quite unlike one another, but it has been seen 

 that they all rest upon the same principle, namely, that of alter- 

 nating diminution of surface (contraction) and increase of surface 

 (expansion) by means of a rearrangement of the particles of the living- 

 substance. That in amoeboid movement this shifting of the particles 

 is wholly without rule, while in muscular and ciliary movements 

 it is orderly, proves only that the two latter represent a higher 

 stage of differentiation than the former. That, however, they 

 stand in the closest genetic connection with amoeboid movement, 

 that they have become evolved from it phylogenetically, is proved 

 by numerous cases of transition, on the one hand between 

 amoeboid and muscular movement, and on the other between 

 amoeboid and ciliary movement. Engelmann ('81, 2) has found 

 rhizopods (Acanthoeystis) possessing straight, filose, unbranched 

 pseudopodia, which are capable of contracting longitudinally with 

 excessive rapidity, and from which a small muscle-fibre is distin- 



fuishable only by its constant differentiation: Engelmann has 

 ttingly termed these pseudopodia myopodia. Moreover, man} 

 cases have been observed where filose pseudopodia of amoeboid 

 cells carry out pendular vibrations, at first irregularly and slowly, 

 later rhythmically, until they have developed into genuine, 

 constant cilia. In view of such facts no proof is needed to 

 place beyond doubt the genetic connection of the three forms of 

 contraction, even if careful observation of their single factors had 

 not proved sufficiently clearly the identity of the principles upon 



