400 ON THE ORIGIN, PROPAGATION, 



That the matter expectorated by phthisical patients 

 is infectious had been placed by previous investigations 

 beyond doubt. The principal question set before him- 

 self by Cornet had reference to the part played by the 

 air in the propagation of lung disease : Is the breath 

 of persons suffering from phthisis charged, as assumed 

 by some, with bacilli ? or is it, as assumed by others, 

 free from the organism? The drawing of the air 

 through media able to intercept its floating particles, 

 and the examination of the media afterwards, might, at 

 first sight, appear the most simple way of answering 

 this question. But to examine a thousand litres of air 

 would require a considerable time, and this is only one- 

 twelfth of the volume which a man breathing quietly 

 expires every day. If the air were only sparingly 

 charged with bacilli, the amount necessary for a 

 thorough examination might prove overwhelming. 

 Instead of the air, therefore, Cornet chose for examina- 

 tion the precipitate from the air ; that is to say, the 

 dust of the sick room) which must contain the bacilli 

 in greater numbers than the air itself. 



He chose for his field of operations seven distinct 

 hospitals (Krankenhauser), three lunatic asylums (Ir- 

 renanstalten), fifty-three private houses, and various 

 other localities, including private asylums, lecture- 

 rooms, surgical wards, public buildings, and the open 

 street. The smallness of the bacilli has given currency 

 to erroneous notions regarding their power of floating 

 in the air. The bacilli are not only living bodies, but 

 heavy bodies, which sink in water and pus, and fall 

 more rapidly in calm air. Cornet gathered his dust 

 from places inaccessible to the sputum issuing directly 

 from the coughing patient. He rubbed it off high- 

 hung pictures, clock-cases, the boards and rails at the 

 back of the patient's bed, and also off the walls behind 



