155 



63]. Concerning other blood-sucking insects, the hog louse, Haemato- 

 pinus siiis, failed to give a therniotropic reaction, but this is not 

 astonishing since these parasites live permanently on their host, and, 

 being wingless, would hardly be able to find their host by means of a 

 tropism. 



Newcomb (C). On an Outbreak of Relapsing Fever in Turkey in 



19iS.— Indian Med. Gaz., Calcutta, Iv, no. G, June 1920, pp. 208- 

 217. 



The outbreak of recurrent fever in Turkey, which made its appear- 

 ance in April 1918 and continued until June, was undoubtedly due to 

 lice. The literature on relation of this disease to lice and other insects 

 is reviewed. 



Facer (A. W.). Hints on Dips and Dip-Testing. — Rhodesia Agric. Jl, 

 Salisbury, xvii, no. 3, June 1920, pp. 255-261. 



Dipping is a convenient method of poisoning ticks with arsenic, and 

 the effective and safe solutions for dipping at different intervals are : — ■ 

 0*08 per cent, arsenious oxide for 3-day dipping ; 0-16 per cent, for 

 7-day dipping ; 0*24 per cent, for 14-day dipping. Solutions that are 

 much weaker than the above for the prescribed intervals do not kill the 

 ticks ; solutions that are much stronger for the prescribed intervals 

 are dangerous, in that the cattle may be scalded in passing through 

 them, perhaps with fatal results. 



In testing dips the object is to find the percentage of arsenious oxide 

 in the tank fluid, which in practice contains water, dirt, soda, arsenious 

 oxide, and various other substances added to render the fluid bitter 

 to the taste, etc. Arsenious oxide possesses the property of absorbmg 

 iodine in a certain definite proportion (2 oz. absorb about 5 oz.). The 

 arsenious oxide in dips can therefore be found by testing a measured 

 quantity of it with a " testing solution " of iodine of a definite strength. 

 As the soda would interfere, it is removed by adding sulphuric acid 

 (about 30 drops per bottle). When enough acid has been added the 

 sediment usually settles, and the clear liquid can be poured off, or if 

 necessary it can be filtered. Exactly 50 c.c. of this liquid is measured 

 off. The acid it contains is counteracted by adding sodium bi-carbon- 

 ate until there is no further effervescence. A little Gloy is then added. 

 Gloy contains dissolved starch, which gives a blue colour with the 

 slightest trace of " free iodine." The dipping fluid is now ready for 

 testing. The iodine solution is placed in a burette, so that the amount 

 used can be measured, and gradually introduced into the beaker 

 containing the fluid, the latter being thoroughly and constantly shaken 

 during the process. 



As the addition of the iodine proceeds the blue colour appears, 

 but rapidly disappears on shaking. After a time it disappears much 

 more slowly, and the iodine should then be introduced only a very 

 little at a time until the blue colour persists when the fluid is thoroughly 

 shaken. The number of cubic centimetres absorbed by the dip is then 

 read from the burette. By dividing this number by 100 (when exactly 

 50 c.c. of dip have been taken for the test) the amount per cent, of 

 arsenious oxide in the dipping fluid is found. 



