60 Transactions. — Miscellaneous. 



The apparatus used for tlie purpose is so constructed as to 

 enable the observer to collect, on thm plates of glass coated 

 with glycerine, the particles of dust, &c., floating in the at- 

 mosphere, the collecting-plates being transferred, at fixed 

 intervals, to the objective of a microscope in order that the 

 collected matter may be examined. By means of this process 

 calculations have been made in the various places of observa- 

 tion of the number of microbes or their spores ordinarily pre- 

 sent in given volumes of air, and it has been found that 

 during the damp weather of the winter months, and that part 

 of the sunnuer in which the increased temperature is accom- 

 panied by moisture, they are comparatively few in number, 

 the maximum being reached in the months of April, May, and 

 June, (answering to our months of October, November, and 

 December,) when the summer air is hot and dry, and during 

 cold dry weather in winter, the chief reason for the observed 

 difference in numbers being that during the moister seasons 

 the microbes and their spores settle on the ground, on the 

 leaves of plants, &c., where, however, the pathogenic forms 

 are to the full as dangerous as when floating in the atmo- 

 sphere. The difference in the number of spores found by 

 means of these observations imder favourable and mifavour- 

 able conditions was considerable, the number under the 

 former frequently reaching 35,000 in a cubic metre of air, 

 whilst under the latter it did not exceed 7,000. But, whether 

 we take into consideration the higher or the lower number, it 

 is clear that the risk of infection is extremely great, especially 

 in places where diseases originating from the introduction of 

 these organisms into the system are known to exist. 



As instances of the extreme danger resulting from such 

 conditions I might cite the case of hospitals in which large 

 numbers of patients formerly died in consequence of erysipelas 

 supervening upon surgical operations, owing to the atmo- 

 sphere being thickly pervaded with the microbes of that disease, 

 and the case of whole families having been sacrificed, chiefly 

 through ignorance, but too often through that pig-headed dis- 

 regard of the results of scientific investigation which persons, 

 otherwise intelligent, frequently display in relation to such 

 diseases as phthisis and small-pox. Fortunately, as regards 

 our hospitals, the disastrous results produced by erysipelas are 

 now avoided by the use either of Guerin's protective dressing — 

 adopted in consequence of Tyndall and Pasteur's researches 

 into the nature of air-germs — or, as is more generally the case, 

 of Lister's antiseptic treatment of wounds. 



It will have been gathered from the foregoing remarks 

 that the microbes of the various diseases I have already re- 

 feri-ed to — which, however, by no means exhaust the list of 

 those that owe their origin to the action of pathogenic germs — 



