Cattle-Fever Ticks. 29 



REPLENISHING THE BATH AND CORRECTING ITS STRENGTH. 



As dipping goes on the bath naturally needs replenishing, and its 

 strength probably needs correction from time to time. The causes 

 which may lead to changes in the strength of arsenical baths, to- 

 gether with methods for making chemical tests, have been discussed 

 elsewhere.^ Before leaving the vat after dipping one may measure the 

 depth of the bath or mark its level on the side of the vat. But even then 

 at the next dipping one can not be certain just how much a change 

 of level has affected the strength of the bath. For instance some of 

 the bath may have leaked out from the bottom while rain water has 

 run in from the top. Furthermore certain microorganisms can grow 

 in the bath in spite of the presence of the poisonous arsenic, and can 

 greatly affect its strength. As already mentioned, the active ingre- 

 dient of the bath is sodium arsenite. The microorganisms in the proc- 

 ess of growth can transfer oxygen from the air to the sodium 

 arsenite, thus converting it to sodium arsenate, a distinctly different 

 compound of arsenic and much less poisonous to ticks. 



The rate at which a bath may lose strength through oxidation de- 

 pends on conditions and is very variable, but ordinarily is sufficiently 

 rapid to weaken the bath decidedly in a month or two. There is, 

 also, a certain species of microorganism wdiich can grow in baths 

 through which large numbers of cattle are passed frequently and 

 wdiich operates in precisely the opposite manner froui those men- 

 tioned above, namely, by reducing arsenate to arsenite, thus render- 

 ing the bath stronger. 



It is therefore plain that the only sure way to get proper results 

 from successive dippings in the same bath is to make a chemical test 

 of its strength shortly before each dipping. The Bureau of Animal 

 Industry provides all officials engaged in cooperative eradication 

 work with outfits for making this test. It is easily carried out by a 

 properly qualified person, and the cattle ow^ner who dips privately 

 should have his baths tested in the same way. If a sample must be 

 sent away for test certain precautions are necessary. First stir the 

 bath well. Fill the bottle (not less than one-fourth pint) nearly to 

 the neck and at once carefulh' add concentrated f ormaldehyde - 

 (which is cheap and can be obtained from a druggist) with a medi- 

 cine dropper in the proportion of 5 drops to each one- fourth pint. 

 Cork tightly and send at once. 



No anxiety need be felt regarding the accumulation of oxidized 

 arsenic in the bath during a single season's use. Experiments by the 

 Bureau of Animal Industry have shown sodium arsenate to be far 



1 U. S. Department of Agriculture Bulletins 7G and 259. 



- This is to act as a preservative against microorganisms, wbicli may act mucli more 

 '\J rapidly in a small sample than in the original bath in its comparatively cool location 

 ■^ underground. 



