The Air of Sewers. 



519 



These results are very decided, and confirm and extend for micro- 

 organisms the results obtained by Professor Frankland for lithia 

 solutions. They show conclusively not only that micro-organisms are 

 disseminated in sewer air by splashing, but that those having this 

 origin may be carried to a considerable distance along a sewer or 

 drain-pipe. Calculating from these experiments, air vitiated as 

 above described, and to a similar extent, would still contain about 

 400 micro-organisms per litre after travelling about 60 yards, in a 

 sewer 5 feet high, and with a draught of about 1 foot per second. It 

 is therefore of the greatest importance that sewers and drains should 

 be so arranged as to avoid splashing as much as possible. 



TJie Physiological Effects of Unorganised Organic Matter in Sewer Air. 



In view of the fact that ordinary sewer air, in the absence of splash- 

 ing, turned out to be to all appearances comparatively innocent as 

 regards its micro-organisms, and assuming that it has an injurious 

 effect on health, we directed further attention to the unorganised 

 organic matter present in it. Of organic compounds most likely to 

 produce some of the bad effects ascribed to sewer air, volatile 

 ptomaines* at once suggest themselves, on account of the intensely 

 poisonous properties possessed by various known ptomaines. f We 

 therefore endeavoured to ascertain whether sewer air contains any 

 poisonous volatile bases. For this purpose air was drawn continuously 

 for thirty-four days from the sewer side, below the trap, of an earthen 

 pipe, which acted as the drain from the College water-closets and 

 urinals. This air was bubbled continuously through very dilute sul- 

 phuric acid, in order that any basic substance which the air contained 

 might be retained. The solution thus obtained was subsequently 

 neutralised exactly with ammonia, and evaporated to dryness on a 

 water-bath. The residue was dissolved and injected subcutaneously 

 into rabbits, but produced no effect whatever, even in doses of a 

 gram of the dry substance. Evidently if there was any poisonous 

 substance in the air, it was not contained in the residue injected. 

 Unfortunately this experiment is not conclusive, on account of the 

 instability of many of the organic bases in question. 



If poisonous organic substances had been present in serious quanti- 

 ties in the air of the sewers we examined, we should presumably have 

 ourselves felt some effects from them, as we were sometimes in the 

 sewers for several hours, more or less continuously. We could never^ 

 observe any bad effects, however, from our stay, although we werQ 

 previously quite unaccustomed to entering sewers. 



* Ptomaines are basic nitrogenous compounds formed by the decomposition of 

 animal or vegetable matter. 



f Cf. Brieger, ' Ueber Ptomaine,' 1885-86. 



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