1878.] Mr. B. T. Lowne on Eyes of Insects. 



261 



To decide wliicli of these explanations is correct, a vessel was filled 

 with spongy iron and distilled waber, the air being expelled from the 

 former as far as practicable. After three months' standing, I analyzed 

 the gas, collected as before by inserting a rod into the spongy iron. I 

 found that it neither contained hydrogen nor carbon, therefore most 

 probably consisted only of atmospheric nitrogen. This appears to in- 

 dicate that the carbon, which was obtained in the previous experiment, 

 is actually the result of the decomposition of organic matter. 



The connexion between disease and impure water, more especially if 

 it be contaminated by putrescent organic matter, has been strongly 

 urged by various authorities, such as Drs. Buchanan, Frankland, 

 Sanderson, Simon, Tyndall, and others. This has led me to 

 attach such importance to the demonstration that "living ferments" 

 are absent from polluted water after filtration through spongy iron. 

 Analytical figures, in their turn, have proved that even Thames water 

 can by filtration through this material be made, chemically speaking, 

 purer than some of the best deep well waters. As the latter are 

 mostly more or less supplied by polluted surface water, which is 

 purified by filtration in passing downwards, there is no reason why 

 they should be preferred to artificially filtered water, provided the 

 physiological character of both proves to be alike. This inquiry is at 

 the present moment being officially instituted in several countries. 

 Trustworthy evidence in the form of actual experience may thus ere 

 long be expected to settle the final question, whether and how far the 

 artificial purification of impure water by spongy iron can be considered 

 a safeguard against the propagation of disease. 



II. " On the Modifications of the Simple and Compound Eyes of 

 Insects." By B. Thompson Lowne, F.R.C.S., Lecturer on 

 Physiology at the Middlesex Hospital Medical School. Arris 

 and Gale Lecturer on Anatomy and Physiology in the Royal 

 College of Surgeons. Communicated by Professor Flower, 

 F.R.S. Received February 27, 1878. 



(Abstract.) 



The simple eyes of insects have been so accurately described by 

 previous observers, that little need be said on their structure. I have 

 described the simple eye of Eristalis, chiefly for comparison with the 

 compound and aggregate eyes. The close relation of the recipient 

 rods to the inner surface of the cornea in this insect is most note- 

 worthy, since, combined with the great convexity of the cornea and 

 the highly refractive nature of the rods themselves, this renders the 

 formation of an optical picture impossible. These facts with the small 



