Movement 

 Movements 



SCIENTIFIC SIDE-LIGHTS 



466 



on after the animal has been mutilated, this 

 movement must therefore continue to pos- 

 sess all the same elements of character 

 which accompanied it when the animal was 

 complete. And not only is the reasoning 

 bad, but as a matter of fact the conclusion 

 has been proved to be erroneous. Farther 

 investigations have shown that when the 

 cerebral hemispheres have been removed the 

 *' reflex action " in a frog's leg acquires a 

 new character. It becomes a mere result 

 of physical causation, and is consequently 

 as certain and inevitable as the action of 

 a coiled spring. Accordingly, it can be pre- 

 dicted and foreseen with certainty. In short, 

 the mental element has been . eliminated 

 along with that part of the machinery which 

 is the organ of consciousness and will. But 

 when that part of the machinery remains 

 untouched, then " reflex action " loses its 

 character of necessity as the result of mere 

 mechanical causation. It cannot be pre- 

 dicted with certainty, because altho the 

 " stimulus " may be the same, and the ani- 

 mal impulse may be the same, there is a 

 controlling apparatus to which has been 

 given the free and incalculable power of 

 resisting both stimulus and impulse. Both 

 parts of the apparatus are equally machin- 

 ery. But the one has a mental function, and 

 the other has a function purely physical. 

 ARGYLL Unity of Nature, ch. 3, p. 65. 

 (Burt.) 



2285. MOVEMENT, SUSTAINED, 

 WITH SLIGHT EXERTION The Condor's 

 Flight. When the condors are wheeling in 

 a flock round and round any spot, their flight 

 is beautiful. Except when rising from the 

 ground I do not recollect ever having seen 

 one of these birds flap its wings. Near 

 Lima I watched several for nearly half an 

 hour without once taking off my eyes ; they 

 moved in large curves, sweeping in circles, 

 descending and ascending without giving a 

 single flap. As they glided close over my 

 head I intently watched from an oblique 

 position the outlines of the separate and 

 great terminal feathers of each wing; and 

 these separate feathers, if there had been 

 the least vibratory movement, would have 

 appeared as if blended together; but they 

 were seen distinct against the blue sky. 

 The head and neck were moved frequently 

 and apparently with force; and the ex- 

 tended wings seemed to form the fulcrum 

 on which the movements of the neck, body, 

 and tail acted. If the bird wished to de- 

 scend, the wings were for a moment col- 

 lapsed; and when again expanded with an 

 altered inclination the momentum gained by 

 the rapid descent seemed to urge the bird 

 upwards with the even and steady move- 

 ment of a paper kite. In the case of any 

 bird soaring, its motion must be sufficiently 

 rapid so that the action of the inclined 

 surface of its body on the atmosphere may 

 counterbalance its gravity. The force to 

 keep up the momentum of a body moving 



in a horizontal plane in the air (in which 

 there is so little friction) cannot be great, 

 and this force is all that is wanted. The 

 movement of the neck and body of the con- 

 dor, we must suppose, is sufficient for this. 

 However this may be, it is truly wonderful 

 and beautiful to see so great a bird, hour 

 after hour, without any apparent exertion, 

 wheeling and gliding over mountain and 

 river. DARWIN Naturalist's Voyage around 

 the World, ch. 9, p. 186. (A., 1898.) 



2286. MOVEMENT UNIVERSAL IN 

 PLANTS Generally Spiral in Character 

 Circumnutation. The most widely preva- 

 lent movement is essentially of the same 

 nature as that of the stem of a climbing 

 plant, which bends successively to all points 

 of the compass, so that the tip revolves. 

 This movement has been called by Sachs 

 " revolving nutation " ; but we have found 

 it much more convenient to use the terms 

 circumnutation and circumnutate. As we 

 shall have to say much about this move- 

 ment, it will be useful here briefly to de- 

 scribe its nature. If we observe a circum- 

 nutating stem, which happens at the time 

 to be bent, we will say, towards the north, 

 it will be found gradually to bend more 

 and more easterly, until it faces the east; 

 and so onwards to the south, then to the 

 west, and back again to the north. If the 

 movement had been quite regular the apex 

 would have described a circle, or rather, as 

 the stem is always growing upwards, a cir- 

 cular spiral. But it generally describes ir- 

 regular elliptical or oval figures; for the 

 apex, after pointing in any one direction, 

 commonly moves back to the opposite side, 

 not, however, returning along the same line. 

 Afterwards other irregular ellipses or ovals 

 are successively described, with their longer 

 axes directed to different points of the com- 

 pass. Whilst describing such figures the 

 apex often travels in a zigzag line, or makes 

 small subordinate loops or triangles. In 

 the case of leaves the ellipses are generally 

 narrow. DARWIN Power of Movement in 

 Plants, ch. 1, p. 1. (A., 1900.) 



2287. New Results 



Reached by Ceaseless Striving Effects of 

 Circumnutation. Apparently every growing 

 pirt of every plant is continually circumnu- 

 tating [see 2286], tho often on a small scale. 

 Even the stems of seedlings before they 

 have broken through the ground, as well as 

 their buried radicles, circumnutate, as far 

 as the pressure of the surrounding earth 

 permits. In this universally present move- 

 ment we have the basis or groundwork for 

 the acquirement, according to the require- 

 ments of the plant, of the most diversified 

 movements. Thus, the great sweeps made 

 by the stems of twining plants, and by the 

 tendrils of other climbers, result from a 

 mere increase in the amplitude of the or- 

 dinary movement of circumnutation. The 

 position which young leaves and other or- 

 gans ultimately assume is acquired by the 



