254 THE AVORLD OF LIFE 



CHAP. 



There is, however, a more general explanation even than 

 this, and one that applies to what has always been held to 

 be the most difficult of all — that of the origin of the organs 

 of sense. 



The various sensations by which we come into relation 

 with the external world — sight, hearing, smell, taste, and 

 touch — are really all specialisations of the last and most 

 general, that of material contact. We hear by means of a 

 certain range of air-waves acting on a specially constructed 

 vibrating organ ; we smell by the contact of excessively 

 minute particles, or actual molecules, given off by certain 

 substances ; we taste by the action of soluble matter in 

 food on the papillae of the tongue ; and we see by the impact 

 of ether-vibrations on the retina ; and as other ether-vibra- 

 tions produce sensations of cold or warmth, or, when in excess, 

 acute pain, in every part of the body, the modern view, that 

 matter and ether are fundamentally connected if not identical, 

 seems not unreasonable. 



Now, as all our organs of sense, however complex, are 

 built up from the protoplasm which constitutes the material 

 of all living organisms, and as all animals, however simple, 

 exhibit reactions which seem to imply that they have the 

 rudiments of most, if not all of our senses, we may conclude 

 that just in proportion as they have advanced in complexity 

 of organisation, so have special parts of their bodies become 

 adapted to receive, and their nervous system to respond to, 

 the various contacts with the outer world which produce 

 what we term sensations. There is therefore, probably, no 

 point in the whole enormous length of the chain of being, 

 from ourselves back to the simple one-celled Amoeba, in which 

 the rudiments of our five senses did not exist, although no 

 separate organs may be detected. Just as its whole body 

 serves alternately as outside or inside, as skin or as stomach, 

 as limbs or as lips, so may every part of it receive a slightly 

 different sensation from a touch outside or a touch inside,; 

 from an air-vibration or from an ether-vibration, from those 

 emanations which affect us as noxious odours or disgusting 

 tastes. But if this view is a sound one, as I think it will be 

 admitted that it is, how absurd is it to ask, " How did the eye 

 or the ear begin ? " They began in the potentiality of that 



