8 SCIENCE PROGRESS. 



recollected that the formation of a hemihedral crystal is 

 very probably accompanied by electric pressure, and a 

 sudden crystallisation might be the source of the discharge. 

 That some crystalline structure seems visible in muscular 

 fibre might lend plausibility to this suggestion, though the 

 enormous prevalence of diffusion and superficial layer 

 phenomena in organic bodies makes the former a more 

 probable line of investigation, muscular contraction itself 

 being either a diffusion or superficial tension phenomenon. 

 In any case, the openings for means of communication 

 between physics and biology are evidently innumerable, 

 and many of them ripe for opening up. The curious 

 preferences for dyes shown by organic bodies is possibly 

 another example of these superficial affinities, where the 

 question of relative solubility in the superficial layer depends 

 on how much the superficial tension is changed by the body 

 dissolved, and so may depend not only on the solvent but 

 on the nature of the neighbouring surface. Many interest- 

 ing questions depending on the size of molecular groups, 

 which we learn from the theory of gases, are of great 

 biological interest. Why do small solid particles, suspended 

 in a liquid, keep continually moving about? If this motion 

 be not part of the heat energy of the liquid, where does 

 the energy required to keep them moving come from ? 

 If it is part of the irregular heat energy of the liquid, it 

 would appear as if the microscopist, with a fine needle, 

 might act the part of a Maxwelian demon, and by a 

 proper sorting of the particles frustrate the second law 

 of thermodynamics. It has been suggested that this is 

 actually done by minute organisms. This does not, how- 

 ever, at present look like a very hopeful supply of work, 

 though there is no knowing what we may come to when 

 coal fails us. In any case, this whole subject of the possible 

 structural complexity of visible particles is an important road 

 between physics and biology, about which enough is known 

 to make advance possible. The road through the special 

 senses of sight and hearing has been nobly pioneered, 

 though many branches of it require much strengthening. 

 The whole subject of electric stimuli, the electric currents 



