FORM AND LIFE. 521 



Nature. Energy as considered in physics, apart from chemistry, 

 has been classified in various forms, viz., energy of motion (trans- 

 lation or rotation), strain, vibration, heat, radiation, electrification, 

 electricity in motion, magnetization, and gravitative separation. 

 Those forms which are represented directly by bodies (whether 

 extended masses or molecules) in motion or deformation, and 

 which do not appeal to our special senses for recognition, consti- 

 tute mechanical energy. The first two named above are plainly 

 such, and all the others except the last have been shown to be 

 such indirectly ; it is generally believed that the last will be found 

 to be reducible to the same form, so that probably all are essen- 

 tially mechanical, and physicists are hoping to reduce them all to 

 the mechanical as the ultimate form of energy. The importance 

 to the physicist, therefore, of an acquaintance with the principles 

 of mechanics can not be overestimated : without such an acquaint- 

 ance his efforts to unravel the mysteries of physical science or to 

 gain possession of its secrets will be futile. 



FORM AND LIFE. 



BY M. GEORGES POUCHET. 



IN the first glance over Nature, everything living, every plant 

 or animal, and every part of what lives, seems to have a defi- 

 nite shape ; and we are naturally led to regard form in organized 

 beings as an essential attribute of life. On the other hand, gases, 

 which spread out into infinity ; liquids, molding themselves on 

 the walls of the vessels that stop their flow ; rocks, cut into a 

 thousand shapes without ceasing to be the same rock show us an 

 inorganic world almost wholly freed from the fatality of form. 

 Crystals, indeed, seem to form an exception to this. They also 

 have limited shapes, with contours even much better defined than 

 those of life ; but when we bray them in a mortar, they are still 

 always the same body, and the same chemical species, even though 

 they are no longer crystals. A living being, sugar cane or beet 

 root, rasped or reduced to pulp, has no longer anything of itself. 

 It has ceased to be, and no power can, from the pulp, build the 

 organism back into its former shape. But we can reconstruct the 

 crystal, and draw it anew from its dust. 



The living being, considered in itself, independently of the be- 

 ing from which it is derived and those which will be derived from 

 it, is, in its way, with some exceptions, a sort of atom, an indivisi- 

 ble whole. Hence that very just denomination of individual, to 

 designate the being endowed with life. 



What we call species in speaking of plants and animals is 



