La Iniciación · Año V, Nº 45 · January 1946

1rises the value of a number is the quantity of units contained in it, so also what characterises an energy is the quantity of its vibratory units — that is, its wavelength.

2Nor shall we occupy ourselves here with all the phenomenology to which light gives origin and with which Optics deals: refraction, reflection, filtration, absorption of determinate rays and reflection of others according to the nature of the object on which they fall, etc. We note only, in this regard, that if light comes to impress the retina and thus render possible the phenomenon of vision, it is owing to the fact that the cones and rods are contrived to be sensitised exclusively by waves oscillating between 800 and 400 micromicrons — that is, by waves of white light. [Sic: the Spanish prints contraídos and sor.]

3The phenomenon is, then, analogous to that of the resonance of sound waves.

4It is clear that if the construction of our retina were different from what it is, we could perceive waves of a length different from what we commonly perceive, and thus have the possibility of knowing the world around us under a new aspect.

5The biological influence of light manifests itself in thermal effects and in chemical effects — and it is prevalently the latter that have great importance in the development of biological phenomena.

6The thermal effect is produced above all by wavelengths which, in the spectrum, oscillate between the violet and the red, and reaches its maximum in the ultra-red.

7The chemical effect increases from the red toward the violet and reaches its maximum in the ultraviolet.

8This effect is, then, as can be seen, the inverse of the preceding.

9By the interposition of absorption media it is possible to eliminate certain radiations.

10Thus, for example, a red filter lets pass especially radiations of chemical effect, and a blue filter permits a weak chemical action and eliminates almost completely the thermal action. [Editorial gloss: so printed; the two filters' roles read as transposed.]

11Owing to those thermal and chemical actions, light is indispensable for the greater part of living beings.

12I say the greater part, because exceptions exist — such as certain fungi that live only in darkness, and marine animals living in the abysses where light does not reach.

13The influence of light on minerals is amply known.

14All who have elementary knowledge of chemistry know that numerous substances exist that change their chemical properties if exposed to light: silver nitrate blackens; many others must be kept in yellow vessels to preserve them from the action of light.

15The influence of light on vegetables is likewise well enough known, and we know it has great importance for the life of plants.

16The phenomena of photo- and heliotropism are known: plants that open their flowers to the light of day and close them at night.

17It is owing to the action of light that photosynthesis, or the assimilation of carbon, is effected in the vegetable organs containing chlorophyll.

18The distinct geographical distribution of vegetables demonstrates clearly how they use the thermal effect of light.

19The influence of light on animals and man is also, in great part, known.

20On the inferior organisms and bacteria, light is in general unfavourable and, if it is fairly intense, can go so far as to kill.

21Its bactericidal and anti-fermentative action (attenuating the toxic products elaborated by them) has already been used as a means of sterilisation.

22If a culture medium is exposed to light and the bacteria are afterwards placed in it, they do not develop — which demonstrates that the effect of light is also posthumous and indirect. · 17

Our translation, period-faithful. Citable as our translation, never as the source.