482 



although there is no evident connecting medium between them, nor, 

 generally, any continuity of structure. 



I cite these two instances the ciliary motion and the contraction 

 of the vacuoles or vesicles in the minute Algae, as the simplest 

 examples of rhythmic movements simplest in regard of method, of 

 structure, of apparent uniformity of circumstances, and of spontaneity. 

 And if I were to enumerate all the instances of rhythmic motion that 

 I can find, other than those of hearts, their variety would suffice to 

 show, that for the explanation of rhythm, we must find something 

 much wider than any peculiarity in the structure or nerve-supply of 

 hearts. The time-regulated movements of Oscillatorise and their 

 congeners ; those of the lateral leaflets in Desmodium gyrans, and 

 of the labellum in Megaclinium falcatum * ; the movements of 

 spermatozoa and of their analogues in the vegetable kingdom ; the 

 constant rhythm of the nutritive yelk in the ovum of the Pikef ; the 

 movements of the pulmograde Acalephse ; the rhythmic actions of 

 the larger veins in the Bat's wing : all these make a heterogeneous 

 list if we look to structure or to office ; their only apparent mark 

 of resemblance is that they are all rhythmical in action, i. e. they 

 all observe a rule of time in the manner of their action, a rule in 

 which there is a regulation not only of the times at which successive 

 and alternate actions follow one another, but of those during which 

 each action is continuous. 



But there is another thing common to all rhythmically acting 

 organs : they are all the seats of nutritive processes ; and I believe 

 that their movements are rhythmical, because their nutrition is so ; 

 and rhythmic nutrition is, I believe, only a peculiar instance, or 

 method of manifestation, of a general law of Time as concerned in all 

 organic processes. In other words, I believe that rhythmic motion 

 is an issue of rhythmic nutrition, i. e. of a method of nutrition, in 

 which the acting parts are at certain periods raised, with time- 

 regulated progress, to a state of instability of composition, from which 

 they then decline, and in their decline may change their shape, and 

 move with a definite velocity, or (as nervous centres) may discharge 

 nerve-force. 



Regarded as phenomena of nutrition, the chief things in which 



* Lindley ; and Morren in the 'Annales des Sciences Naturelles.' 

 t Reichert in Mullen's 'Arcbiv,' 1857, p. 46. 



