1859.] on the Chronometry of Life. 121 



Gonium. In the Croonian Lecture at the Royal Society, in 1857, the 

 speaker had endeavoured to prove that these and other rhythmic move- 

 ments in plants, as well as animals, are due to corresponding time- 

 regulated nutrition. He had expressed his belief 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." And this would be still maintained ; but whether it were 

 true or not, the rhythmical nutrition of rhythmically acting muscles 

 would be certain. If not a cause, it must be a consequence of such 

 acting ; for it is inconceivable that the heart (for example) or the 

 diaphragm, or any other rhythmic muscle, should be free from waste or 

 impairment in its action, or from the necessity of being renovated in its 

 rest. Difference of mode of action could not determine a difference 

 in the immediate effect of action. With long exercise, muscles become 

 so changed that their changed state can be felt in the sensation of 

 weariness, and proved by chemical analysis. But the change thus 

 proved is only the accumulation of the changes wrought in many 

 muscular actions, each of which has contributed a share to the whole 

 amount, just as each revolution of a wheel contributes to the final wear- 

 ing out. Similarly, every action of the heart, or of the breathing 

 muscles, is attended with change or impairment of composition ; but, 

 the impairment is repaired in the next following period of rest or 

 relaxation. In other words, the alternating actions in shortening, and 

 rests in lengthening, of the muscular fibres are correlative and 

 synchronous with their alternating impairments and repairs of compo- 

 sition. The chronometry of such organic processes seems perfect ; 

 nutrition is in them divided, as it were, into units ; and for each unit, 

 there might be reckoned a unit of time. 



Two results of this constant maintenance of rhythmic muscles are 

 remarkable ; namely, the enormous power they are capable of exerting, 

 and their freedom from fatigue when only naturally acting. The latter 

 result is proved to depend on the constant maintenance of the muscles, 

 in their timely intervals of rest, by the weariness which is produced in 

 the same muscles when they act otherwise than rhythmically, as in the 

 muscles of respiration when employed in any voluntary movements, or 

 in coughing or other violent respiratory acts. 



The instances adduced thus far might supply examples of organic 

 processes adjusted to periods of time varying from the length of human 

 life to less than a second. They were all examples of large classes of 

 facts, from which might be filled up the instances of observance of 

 other and very diverse periods of time ; and in all of them, the time- 

 rate is essentially determined, not by external conditions (though these 

 may, in some measure, modify it) but by the inherent properties of the 

 organic bodies themselves. 



In another large group of instances, those, namely, in which vital 

 processes are completed, or attain some climax, in a year or in a set 



