THE DIRECTION OF MOTION. 243 



the sides. I have not, however, satisfied myself that this 

 holds good in all cases." 



Without endorsing all Mr. Hinton's illustrations, to 

 some of which exception might be taken, his conclusion 

 may be accepted as a large instalment of the truth. It is, 

 however, to be remarked, that in the case of organic growth, 

 as in all other cases, the line of movement is in strictness 

 the resultant of tractive and resistant forces; and that the 

 tractive forces here form so considerable an element that 

 the formula is scarcely complete without them. The shapes 

 of plants are manifestly modified by gravitation : the direc- 

 tion of each branch is not what it would have been were the 

 tractive force of the Earth absent; and every flower and 

 leaf is somewhat altered in the course of development by the 

 weight of its parts. Though in animals such effects are less 

 conspicuous, yet the instances in which flexible organs have 

 their directions in great measure determined by gravity, 

 justify the assertion that throughout the whole organism 

 the forms of parts must be affected by this force. 



The organic movements which constitute growth, are 

 not, however, the only organic movements to be interpreted. 

 There are also those which constitute function. And 

 throughout these the same general principles are discern- 

 ible. That the vessels along which blood, lymph, bile, and 

 all the secretions, find their ways, are channels of least re- 

 sistance, is a fact almost too conspicuous to be named as an 

 illustration. Less conspicuous,- however, is the truth, that 

 the currents setting along these vessels are affected by the 

 tractive force of the Earth: witness varicose veins; wit- 

 ness the relief to an inflamed part obtained by raising it; 

 witness the congestion of head and face produced by stoop- 

 ing. And in the fact that dropsy in the legs gets greater by 

 day and decreases at night, while, conversely, that oedema- 

 tous fullness under the eyes common in debility, grows 

 worse during the hours of reclining and decreases after get- 

 ting up, shows us how the transudation of fluid through 



