58 



THE MECHANICAL FUNCTIONS. 



these is, in different cases, almost infinitely varied. A dor- 

 mant vitality may, indeed, exist in a system of organs which 

 have been brought into a perfectly dry state: as is proved 

 by the examples of vegetable seeds, and also of many spe- 

 cies of animalcules, and even of some of the more highly 

 developed Jinnelida, or worms, which may he kept in a 

 dry state for an indefinite length of time, and when moist- 

 ened with water, resume their activity, as if restored to life. 

 The germination of seeds under these circumstances is matter 

 of common observation; but the revivification of animal- 

 cules is a more curious phenomenon, for it takes place more 

 rapidly, and is more striking in its results. The Rotifer 

 redivivus, or wheel animalcule,* (Fig. 1,) which was first 

 observed by Lewenhoeck, and was afterwards rendered ce- 

 lebrated by the experiments made upon it by Spallanzani.. 

 can live only in water, and is commonly found in that which 

 has remained stagnant for some time in the gutters of houses. 

 But it may be deprived of this fluid, and reduced to perfect 



dryness, so that all the functions of life shall be completely 

 suspended, yet without the destruction of the vital princi- 

 ple; for this atom of dust, after remaining for years in a dry 

 state, may be revived in a few minutes by being again sup- 

 plied with water. This alternate suspension and restora- 

 tion of life may be repeated, without apparent injury to tlie 

 animalcule, for a great number of times. Similar phenome- 

 na are presented by the Vibrio trilici, (Fig. 2,) or the ani- 



* Vorlicella rotatoria of Ginclin, and Furcularia of Laniuik. 



