3i8 American Quarterly Microscopical Joiirual. 



be destroyed, but diluted. Dr. Richardson, of London, has already 

 proved that disease poisons are only active when used in a certain 

 degree of concentration. Not long ago the writer strongly advocated 

 a system of artificial ventilation to be applied to vessels from 

 yellow fever ports, which was embodied in a communication to 

 the Ne7v York Times, but not published. The arguments were 

 based mainly upon the assumption that any gaseous poison could 

 be readily removed from any part of a ship by a current of air. 

 Should the poison consist of organized germs, this same means 

 would tend to prevent them from finding a lodgment, or, at least, 

 a suitable nidus for rapid growth and multiplication, by maintain- 

 ing a pure air, and drying up the moist places where the fungoid 

 cells would otherwise multiply. 



Our knowledge of the zymotic diseases is still so limited that the 

 only rational means we have of preventing their spread, are those 

 of thorough ventilation. We may, even today, question whether 

 sewer-gas or the effluvia from decomposing animal or vegetable 

 matter have in them any specific disease-germs. This does not 

 seem to be proved on either side. We do not argue that such gases 

 are harmless, but it seems not improbable that their poisonous 

 action may be merely of a chemical nature, rendering the oxygen 

 of the air inactive, and thus preventing the elimination or oxidation 

 of impurities which therefore accumulate in the blood, and en- 

 gender disease. 



If this view be accepted, it will be found to afford a reasonable 

 explanation of the origin of malaria, receiving some support from 

 the fact that this poison, in certain localities, is much more active 

 at night than during the daytime, when the actinic power of the 

 sunlight may counteract its baneful influence upon the oxygen of 

 the air. 



MR. WENHAM'S POSITION REGARDING HIGH BALSAM 



ANGLES. 



{Received July yth, iSyg). 

 To the Editor : 



In your letter to me of June 5th, I am glad to find that you have can- 

 didly put the following direct question, which has not been asked before. 

 *' I wish you would give me a positive reply to this question. Do you 

 claim that no objective has been made with an immersion aperture above 

 82".' This has been attributed to you." I have had to meet a similar 

 imputation in the Transcxctions of the R. M. S. for this month. In the 



