2 BULLETIN 259, U. S. DEPARTMENT OF AGRICULTURE. 
still present in its original quantity but that it had partly changed 
its form and now existed to that extent as sodium arsenate, 1 a com- 
pound, as previously indicated, quite different in many of its proper- 
ties from sodium arsenite. Fuller, 2 who independently discovered 
the phenomenon in the laboratories of the Bureau of Animal Industry, 
went further and showed that the change is essentially brought about 
through the growth of microorganisms in the dipping baths, other 
factors being relatively of little importance. 
After the appearance . of Fuller's paper pressure of other work 
prevented the obtaining of further knowledge along this line except 
what could be gained from the routine examination of samples from 
the field and an occasional desultory experiment. ■ What was thus 
learned, however, indicated that the matter was probably not yet 
thoroughly understood and that at any rate practical studies should 
certainly be undertaken on the progress of the phenomenon of oxida- 
tion as it occurs in dipping vats in the field under varied conditions 
of actual use. The relative efficacy of solutions of arsenite and 
arsenate against ticks and then relative toxicity toward animals 
clipped therein are subjects entirely beyond the scope of this paper, 
but it is universally believed that sodium arsenite is a much more 
powerful tickicide than sodium arsenate, though at the same time 
more poisonous to cattle. It was clearly a matter of importance to 
ascertain how rapidly a change from one form to the other might go 
on in baths in actual use in the field, since such a change is necessarily 
closely related to the regularity of action of a bath upon both ticks 
and cattle. These field studies have been continued during the past 
two years. 
In the meantime further published work has appeared abroad. 
Laws 3 in explanation of certain observations suggested that, in 
addition to the oxidizing organisms already noted which change 
arsenite to arsenate, there may also exist in some baths reducing 
organisms which change arsenate back to arsenite. He also suggested 
the use of some bactericide to prevent oxidation by preventing the 
growth of the bacteria which cause it. Brunnich and Smith,' Wil- 
liams, 5 and Holborow G have made some studies of the obvious ques- 
tions presented. But the p d work so far seems in general 
hardly comprehensive enough to insure the drawing of sound prac- 
tical conclusions, while in any event it is confined to certain foreign 
countries where dipping practice as respects strength of dip and 
i Brunnich (Australian Association ncement of Science, 1909, through Journal of Agricultural 
Science, 1911, vol. 4, p. 177) appears to have been first to make this discovery. 
2 Bureau of Animal industry Circular 182, Xov. 9, 1911. 
s Agricultural Journal of Union of South Africa, 1913, vol. 5, p. 915. 
i Queensland Agricultural Journal, 1914. vol. 2. part I. p. 81. 
5 Agricultural Journal of Union of Sc . 1913, vol. 5, p. 68; 1914, vol. 8, p. 12. 
6 Rhodesia Agricultural Journal, 1914, vol, 11, p. 579. 
