UTILISATION OF RESIDUES OF ESSENTIAL OIL. pigs) 
cultures of the bacillus. All the active components of 
the crude oil were freshly prepared and tested within a 
day or two of their preparation, 
Before submitting the results of the germicidal investi- 
gation it will be as well first to define the Rideal-Walker 
test:—The Rideal-Walker test is the adopted standard for 
determining the germicidal values of disinfectants, germi- 
‘cides and antiseptics. Stated briefly, measured quantities 
of a 24 hours broth culture of B. typhosus are exposed to 
measured quantities of the disinfectant to be tested, for 
definite periods against a standard strength of pure carbolic 
acid. Ainslie Walker adopted 1% as his standard. The 
mixed bacilli and disinfectant are then inoculated into 
tubes of sterile nutrient broth by means of a platinum loop 
at intervals of 24 minutes. The inoculated tubes are then 
incubated at 37° O. for from 24 to 48 hours and are then 
read. Tubes which show a turbidity (i.e., growth) are 
marked with the plus sign, while those which remain clear 
(i.e., no growth) are given the minus sign. Of course the 
action of the disinfectant is due to adsorption in a colloidal 
mixture, much the same as in the dyeing of fabrics, and 
the disinfectant can beexhausted by the addition of sufficient 
bacillary emulsion. 
The first set of tests was made with aqueous suspens- 
ions of the different units. The aldehydic mixtures were 
fairly stable, but it was found to be impossible to arrive at 
any accuracy with regard to the amount of the aldehyde 
taken up by the water. After a number of trials about 
0°5% was found to be the amount without any appreciable 
separation. The suspensions were opalescent in appear- 
ance, and as stated above, fairly stable, i.e., there was 
no separation after a week. Similar difficulties were 
encountered with the phenols. The solid phenol remained 
unchanged in cold water, but on gently warming or placing 
