202 
Theory and Practice of Dipping 
the mode of action of certain organic compounds of arsenic as trvpano- 
cides in the animal body, is very interesting in connection with the 
above mentioned subject, but a discussion of the matter would lead 
us away from the subject matter of this paper; it is being dealt 
with by one of us (W. F. C.) in collaboration with others, in another 
paper now in course of preparation, on the application of arsenical 
dipping to the prophylaxis and treatment of trypanosomiasis in stock. 
In view of the success which has resulted from the detailed study 
of the mode of action of arsenic and other substances, the cumulative 
effect in the cutaneous tissues would appear to be an important and 
interesting problem to follow up. We may say that we hold the view 
that something of this sort does take place as a result of short interval 
dipping, and as soon as the large amount of field work in hand is 
completed, we intend to undertake a systematic investigation of the 
problem. 
For the moment, it is sufficient to know that the arsenic is taken 
into the body and we have evidence, derived from the work on trypano¬ 
somiasis in dipped animals referred to above, that although the quantity 
of arsenic thus absorbed into the circulating blood is insufficient to poison 
ticks, yet it may be present in sufficient quantity to exert a toxic action 
on such pathogenic protozoa as trypanosomes. 
The Quantity of Arsenic applied in Dipping. 
The amount of arsenic left on the animal after dipping may be 
roughly estimated as follows: an average animal, after allowing the 
superfluous dip to drain off, retains about 0-75 gallon. In the case 
of the ‘Laboratory’ dip, 50 gallons of the dip contains 1 lb. of sodium 
arsenite (80 per cent.), giving a concentration of 0-16 per cent, of arsenious 
acid. Three-quarters of a gallon would contain, therefore, 5-4 gms. 
(84 grains) of arsenious acid. Thus, some 5-4 gms. are applied to the 
skin of the animal at each dipping, and at the rate of five-day intervals, 
the amount applied per month would be 32 gms., and under proper 
conditions, this process can be continued for years without causing any 
inconvenience or injury to the stock. The lethal dose of arsenic for 
cattle, according to Kaufmann 1 (see Appendix III), varies from about 
15 gms. to 30 gms.: it follows, therefore, that quantities of arsenic 
which would almost certainly prove fatal to the animal if administered 
internally may be safely applied to the skin by dipping. 
1 Cited by Finlay Dun (1910), Veterinary Medicines—their Actions and Uses, 12th 
ed., Edinburgh, David Douglas, p. 275. 
