W. F. Cooper and H. E. Laws 
201 
That the arsenic accumulates by repeated applications is proved by 
analysis of the skin of animals dipped at short intervals. Watkins- 
Pitchford carried out numerous analyses, the results of which we briefly 
tabulate (see Appendix VI), and our own analyses absolutely confirm 
his findings. He goes on to state (pp. 49-50): 
‘that the value of frequent dipping lies in the sustained effect 
produced rather than in the mechanical destruction of ticks which 
follows immersion in the dip tank, and...this maximum killing 
efficiency of a beast is only to be maintained by the repetition of 
the dip or spray process with such frequency as will compensate 
the skin for the loss of arsenic which is continuously absorbed from 
it and excreted in the urine by a natural process of elimination.... 
The power of an habituated animal to destroy ticks placed upon 
it (or gaining access in the natural manner after dipping) is rapidly 
lost, five or six days’ lapse sufficing to reduce such an animal to 
nearly the same condition as that which exists in the case of an 
unhabituated animal or beast which is dipped at the long interval 
of, say, ten days or a fortnight.’ 
Although Wat ki n s-Pi tch ford expresses the opinion that a five or 
six days’ lapse is sufficient to reduce the resistant powers to that of 
an unhabituated animal, we found, in our work at Elliotdale (see 
Appendix VIII), that, in actual practice, a five-day interval is sufficient 
to keep stock free from East Coast Fever. 
In short, although the fact is not admitted by several eminent 
veterinary authorities, exclusive of those who have carried out investi¬ 
gations on the lines of AVatkins-Pitchford and ourselves, we do not 
consider that this cumulative effect of arsenic applied to the skin is 
open to any reasonable doubt 1 . 
Arsenical solutions applied to the skin penetrate the actual cellular 
tissues by osmosis, and it is reasonable to presume, from what has 
already been said of the cumulative effect in the cutaneous tissues, 
that the arsenic enters into an actual combination with some organic 
constituent of the cells. 
The work of Ehrlich, Nierenstein, Breinl, Levaditi 2 and others, on 
1 In order not to obscure the main points of our paper, we have collected, in the form 
of an appendix, some of the more cogent objections to our theories, together with our 
criticisms (see Appendix IX). 
2 Ehrlich (1908), Verhandl. d. Deutschen dermatolog. Gesellsch. x, Kongress, Juni, 1908. 
Nierenstein (1908), Ann. Trap. Med. and Parasitol. ii, 249-255. Breinl and Nierenstein 
(1909), Zeitschr. f. Immunitatsforscli. v,. exper. Therap. I, 620-632. Levaditi and 
Yamanouchi (1908), C. R. Soc. Biol, lxv, 23. 
