1877.] 



the Effect of Light on Bacteria 



497 



powerful in the direct solar ray, but can be demonstrated to exist in 

 ordinary diffused daylight. 



4. So far as our investigation has gone it would appear that it is 

 chiefly, but perhaps not entirely, associated with the actinic rays of the 

 spectrum. 



5. The fitness of a cultivation-liquid to act as a nidus is not impaired 

 by insolation. 



6. The germs originally present in such a liquid may be wholly 

 destroyed, and a putrescible fluid perfectly preserved by the unaided 

 action of light. 



Although there are many vital phenomena, both of plant-life and of 

 animal, whether in health or disease, to the elucidation of which may be 

 applied this quality of light (now demonstrated, so far as we are aware, 

 for the first time), we have endeavoured in this paper to confine ourselves 

 to the plain facts of our observations, and have studiously avoided specu- 

 lation and theory. We cannot, however, refrain from offering one com- 

 ment on the striking antagonism between these facts and many views 

 that have hitherto prevailed on the relation of light to life. This rela- 

 tion has been principally investigated as regards the chlorophyl-cell ; but 

 chlorophyl may be regarded as simply an organ of nutrition adapted to 

 special circumstances, and differing essentially in its vital phenomena 

 from the true cellular tissue of the plant and its protoplasmic contents. 



It appears to us that the organisms which have been the subject of our re- 

 search may be regarded simply as individual "cells" or minute protoplasmic 

 masses specially fitted by their transparency and tenuity for the demon- 

 stration of physical and other influences. May we not expect that laws 

 similar to those which here manifest themselves may be in operation 

 throughout the vegetable, and perhaps also the animal kingdom wherever 

 light has direct access to protoplasm ? On the one hand we have chloro- 

 phyl, owing its very existence to light, and whose functions are deoxi- 

 dizing ; on the other the white protoplasm, or germinal matter, oxidizing 

 in its relations, and to which, in some of its forms at least, the solar rays 

 are not only non-essential, but even devitalizing and injurious. 



This suggestion we advance provisionally and with diffidence ; nor do 

 we wish to imply that the relations of light to protoplasmic matter are 

 by any means so simple as might be inferred from the above broad 

 statement. 



APPENDIX. 



The artificial solutions employed were similar to those used by Pasteur. 

 The following are the formulae employed : — 



A.— Water, 1500. 



Brown Sugar Candy, 70. 

 Tartaric Acid, 4. 

 Ammonium Nitrate, 4. 



