201 



Effect ok Worms on Pvt-rkscibit.itv— Confinued 



Dates of collection and bottling, October 10-19. 1912. 



Incubation temperature, 20 degrees C. 



Relative stability numbers calculated according to Phelps. 



An examination of the results of all of the experiments made in 

 this connection, of which the above series is a part, shows that the 

 most conspicuous result is the marked increase of putrescibility in the 

 test samples containing the worms as compared with the check samples, 

 which contained no worms. This was a constant feature of all of 

 the experiments. In no case was there an opposite result. The pres- 

 ence of the worms increased the putrescibility under all conditions 

 as regards the presence or absence of the various kinds of suspended 

 matter in the sewage. The reduction time increases with the removal 

 of suspended matter and the difference between the reduction time of 

 the test and that of the check experiments tends to become greater 

 as suspended matter is removed. Increased putrescibility means loss 

 in stability and the loss in relative stability apparently increases with 

 the removal of suspended matter. 



The explanation of the manner in which this increase in putresci- 

 bility is produced by the worms has not been detemiined. The ex- 

 haustion of the oxygen may be accomplished in two ways, ( i ) by the 

 respiratory activity of the worms, and (2) by means of the organic 

 matter contributed in the form of excreta. From a practical stand- 

 point it does not matter by what means the worms reduce the oxygen. 

 The important fact is that the oxygen is being used up. As has been 



