236 IV. STRUCTURAL FACTORS IN A LANGUAGES
stimuli, intensifying them., and so of effecting the most efficient response of the corresponding end-organ.
In our school days we were taught that we have five 'senses'. Modern researches show that there are more than twenty different 'senses'. Besides, as far as 'Smith' is concerned, we know that 'senses' and 'mind' cannot be divided.
The main stimulations which we find in the outside world may be divided into three groups. The first are connected with the roughest macroscopic manifestations of the outside world; they are mechanical impacts which we abstract as 'tactile sensations', which range from a single mechanical contact to rhythmically repeated contacts with our skin as frequently as 1552 vibrations per second. Above this limit 'time?' begin to be registered as a 'duration'; that is, the individuality of 'time/ is lost, and we feel pressure. At this level we deal with gross macro scopic manifestations, which are not only felt but can also be seen.
The second group of manifestations is, in the main, no more on the gross level. Here belong the vibratory manifestations which are no more visible to the unaided eye. We may speak of them as on the microscopic level. They are mechanical vibrations of the air., and we become acquainted with them in the form of sound. The vibrations which the average ear is able to register range from about 30 (sometimes even 12) to about 30,000 or even 50,000 vibrations a second. The ear does not register any other vibrations.*
The third group of vibratory manifestations belongs to a still subtler level. They are elettromagnetic waves of an enormous variety of wavelengths and number of vibrations per second. The lower members of this series are the Hertzian electric waves, the higher members are the X-, or Rontgen-rays. Our nervous systems are capable of registering only a very limited range of these vibrations; namely, the waves called radiant heat, the light waves, and the ultra-violet rays, these last only on a chemical level. It seems that we have no organ which responds directly to electric waves, ultra-violet rays, X-rays, and the many other rays which we know from laboratory work.
Similarly, the chemical 'senses' of taste and smell register only a very small number of actual excitations to which they are exposed.
Animals have different limits of nervous susceptibility, but we can have no idea how the world looks to them unless their nervous system is quite similar to our own. The above statements will become clearer if we tabulate some of them. The following table is taken from An Introduction to Neurology by Professor C. Judson Herrick, p. 85 (Fifth Edition) :
♦Latest researches seem to modify these data.