PRESIDENT^ ADDRESS. 11 



perience in the management of the Society's affairs, since the death 

 of Sir William Macleay, in December, 1891, and the existing con- 

 dition of things has come about in consequence; it was deemed 

 desirable that the alteration of Rule lxiv., so as to provide for a 

 three-fourths majority in the matter of the alteration of the Rules, 

 should receive attention, so that the maintenance of a policy which 

 is founded on precedent as well as experience, should be reasonably 

 safeguarded. 



In the bacteriological laboratory, the Macleay Bacteriologist has 

 continued his research into the action of microbiological life in 

 relation to soil-fertility. In the treatment of domestic sewage, it 

 is pumped over poor soils or sandy wastes, and, in passing 

 through, undergoes an amount of putrefaction, which enables the 

 effluent to be discharged into rivers and harbours. After working 

 actively for some time, the soils become clogged, and are so useless 

 that they have to be rested. In the clogged condition, they are said 

 to be sewage-sick, and it has hitherto been supposed that, in the 

 absence of clay, the inactivity was due to the pores and spaces 

 having become plugged with slime. Recently, however, Russell and 

 Golding have claimed that the sickness is brought about by proto- 

 zoa devouring the decay-bacteria, and preventing their exercising 

 their beneficial function, in consequence of which the soil becomes 

 useless. They were led to this opinion by the fact that, after treat- 

 ment with heat and volatile disinfectants, the surviving bacteria 

 increase in numbers above those in control tests. The experimental 

 work in the Society's laboratory did not support this contention, 

 for when the protozoa were destroyed by a moderate heat, the vola- 

 tile disinfectation was able to bring about a considerable increase 

 in the numbers of the bacteria. That the disinfectant has an 

 action upon the fatty matters in such soils, was shown by the bac- 

 terial growths in the various layers of soil behaving as if the disin- 

 fectant had carried the fatty matters towards the surface while 

 evaporating. The dry sewage-sick soil contained 9 per cent, of 

 organic matter, and 19 per cent, of this consisted of fatty matter, 

 and 9 per cent, of crude gum. The older idea that the inactivity 

 of such soils is due, in the absence of clay, to the accumulation of 



