485 



of the year. In the maturation or the development of an ovum, for 

 example, or in the ripening of seeds, a law of time, various in different 

 species, is observed by all, and their punctuality in arriving at the 

 climax of maturity, after many hours or days or months of progress- 

 ive change, is evidence that they were chronometric in all their 

 course thitherward. And where many such processes are concurrent, 

 though severally independent, as in the contemporary maturation of 

 all the ovules of an ovary, we may say that their concurrence is like 

 that of many exact chronometers ; and their final punctuality, like 

 that of the chronometers, would prove that, in each unit of time, 

 each did a certain and proportionate amount of work. 



In all organic processes, then, there is as minute a regulation of 

 time as there is of quantity, or shape, or quality of matter. Time- 

 work is not a singular characteristic of quickly rhythmic organs ; it 

 is a rule of life ; and its rate in each organism is neither determined, 

 nor beyond certain limits alterable, by external conditions, or by any 

 appreciable qualities of weight or composition (as are the time-rela- 

 tions of inorganic masses) ; but is determined by properties inherited, 

 and inherent in the very nature of the organism, and is least alter- 

 able by external conditions in the highest organisms. 



But though the general law of chronometric nutrition (if I may 

 so call it) may be evident, yet it may be objected by some, that it is 

 proved only for such nutritive processes as are long-continuous and 

 cumulative ; and that it is an unwarranted assumption to think of a 

 rhythmical or frequently interrupted nutrition. To which objection 

 the answer may be, that whether we regard a rhythmic nutrition as 

 the cause of rhythmic motion or not, we are obliged to hold such a 

 method of nutrition as a fact. For we can be nearly certain that in 

 the heart, as in other muscular, or any other parts, the successive 

 impairments and renovations of composition, which constitute the 

 process of nutritive maintenance, are severally accomplished during 

 the successive periods of action and of repose, all exercise being 

 attended with impairment of composition, such as can be repaired 

 only during repose. Now the only repose of the heart's muscles, 

 and I suppose of its nervous system also, is in the brief intervals 

 between their successive actions ; and in these intervals, and, there- 

 fore, with a rhythmic nutrition coordinate with its rhythmical 

 action, the heart-structures must recover from the changes suffered 



