224 PROFESSOR LIONEL S. BEALE, F.R.C'.P., F.R.S., ON 



receives all its nourishment dissolved in water. Nothing 

 that is perfectly dry, lives. The scales of the butterfly's 

 wing, the wings of beetles, flies, etc., and the hard external 

 covering of the legs and claws of insects are dry, but the 

 muscles and nerves, concerned in every movement and 

 in every part that is moved, are always moist. The 

 particular muscular movements and the degree of move- 

 ment, as is in other creatures, depend entirely on the nerves, 

 and nerve centres which are invariably moist. 



It is the nerve " current," which starts from the living 

 matter of the nerve-centre, that determines and regulates 

 the rapidity and degree of contraction of every muscular 

 fibre. The anatomical arrangements are indeed very com- 

 plex, but all nerve action is in its nature vital, and not to be 

 accounted for by physics : but I must not attempt to discuss 

 further this part of the question this afternoon. 



With regard to plants, the proportion of water to the 

 solid matter, especially in the growing state, is enormous. 

 Many succulent vegetables, when fresh, probably consist of 

 as much as nine-tenths of water, and the quantity of actual 

 solid matter in leaves and flowers when dried, is very small. 

 The power of growth in vegetables, as we all know, is 

 wonderful. If you look at the growmg extremities of a 

 root as it makes its way through the moist soil, you always 

 find the tissue very soft from containing much moisture. 

 The active growing extremity of every rootlet consists, indeed, 

 principally of water: but, nevertheless, this soft delicate 

 growing part of the root may gradually make its way, as 

 Ave all know, into furrows or fissures in rock, and even 

 penetrate through some hard substances, and continuing to 

 grow in a moist fissure, it may split very hard wood or even 

 stone, or a very heavy mass may be lifted up. It has been 

 thought that all this active pressure depends on simple 

 imbibition, but no imbibition or absorption of water, as by a 

 porous substance, will account for the facts. A piece of dry 

 Avood driven into a chink in a stone, and then caused to 

 absorb Avater, will perhaps split the stone ; but this is a 

 process A^ery different from that of the pressure exerted by a 

 continually growing root or other part of a plant. By the 

 force of A'igorous liAang groAvth a stone Aveighing a hundred- 

 weight or more may be forced out of its place. Some of the 

 huge gourds of America exhibit this enormous power of 

 growth in a remarkable manner. 



Seeds, you may say, are surely dry. But this is only true- 



