194 
Theory and Practice of Dipping 
pass through the dipping-fluid and be killed. It was found later that, 
after dipping, the stock remain distasteful to ticks for at least two days, 
and, in consequence, the interval was lengthened to five days, and it 
would appear that an interval of seven days may suffice, though this 
has not yet been satisfactorily proved. 
While a solution of sodium arsenite alone causes some inconvenience, 
owing to the fact that stock cannot be used for ploughing and transport 
for one or two days after dipping, the addition of an emulsion to the 
fluid allows the concentration of the sodium arsenite to be considerably 
reduced without decreasing the effectiveness of the dipping-fluid; 
consequently, with the use of such a dipping-wash, the stock suffer no 
inconvenience and the work of the farm is not unduly interfered with. 
At Gonubie Park, some of the oxen have been dipped regularly over a 
period of several years and used continually for trek work and ploughing. 
Horses, mules, etc., also may be dipped regularly, but in the case 
of sheep, it is desirable to retain a separate bath for their use, as the 
loose hairs of previously dipped stock get into the wool and cause 
much trouble and inconvenience in the manufacture of the wool into 
goods. 
Instead of making the cattle swim through a bath, they may be 
driven through a tunnel into which the dipping-fluid is sprayed by means 
of suitably arranged jets, the general principle being that of the ordinary 
‘needle’ bath. The method is not so rapid as the swim bath and there 
is a wide-spread opinion that it is not so thorough in its effects. Never¬ 
theless, the spray bath (Plate XII, figs. 1 and 2) is effective, in spite of 
the objections raised by some authorities. Practically all of Watkins- 
Pitchford’s work was done with this apparatus and we used the method 
in our investigations at Elliotdale. Of those who condemn the spray 
bath, it is generally found that few have had any real experience in 
its use. 
Scalding. By the use of a too concentrated dipping-fluid a more 
or less severe inflammation of the skin is set up, which condition is 
generally referred to as ‘scalding.’ It is not necessarily due to an 
excessive proportion of arsenic in the dipping-fluid; for it may be caused 
by the use of a faulty formula, in which the percentage of arsenic is 
not necessarily excessive, in the preparation of the dip, or by negligence 
in observing certain general principles in the actual operation of dipping. 
These principles are related chiefly to meteorological conditions and to 
the physical condition of the stock at the time of dipping, and as they 
are generally recognised by those who practise dipping and are not of 
