215 



been made recently. There are three theories advanced to account 

 for the death of the tick when poisons are added to the dipping' 

 l^ath: — (1) that the tick absorbs the poison through its 8kin 

 whilst the animal is passing- through the dipping- bath; (2) that 

 the absorption of the poison through the skin of the tick takes 

 place after dipping; and (3) that the beast absorbs the poison into 

 its skin, the tick sucking- in the poison with the juices extracted 

 during the process of feeding-. As reg-ards the first theory, experi- 

 ments were made in which ticks were weighed before and after 

 immersion in water ; the results showed that during- the first hour 

 of immersion, the tick lost in weig-ht. As an animal only takes 

 10-15 seconds to swim throug-h tiie dip, it is impossible that the 

 poison is absorbed by the tick. As reg-ards the second theory, it 

 is thought highly improbable that the absorption of the poison 

 takes place after dipping-, as the fluid dries in less than on hour, 

 during' which period it has been proved that no absorption takes 

 place.'" All evidence supports the third theory, that the tick sucks 

 the poison from the body of the animal with the juices it extracts 

 for food. The author says that local injections of arsenic have 

 caused death to the ticks in that neighbourhood, and althoug-h 

 they did not come in contact with the arsenic, arsenic was found 

 in the body of the tick. The poison injected into the animal's 

 skin does not enter the blood stream, but is taken up by the lymph, 

 which is extracted by the tick. It is necessary therefore that the 

 cattle dip should penetrate the animal's skin uniformly and 

 thoroug-hly. This can only be done by using a dip containing' an 

 oil emulsion. 



Makchoux (E.) & CouvY (L.). Argas et Spirochetes.— A »/?. Inst. 

 Pasteur, Paris, xxvii, no. 6, pp. 45o-tS(), 25th June 1913, 

 15 fig-s, and no. 8, 25th Aug. 191:5, pp. 620-64:1. 



The authors give a summary of the relationship between the 



spirochete and the tick as described by Button and Todd, Leish- 



man, Balfour, Fantham, Blanc and Hindle, and summarise the 



results of their own investigations as follows: — (1) In Argas 



persicus, granules resembling those first described by Leishman 



in Ornithodorus movJxita were found; (2) these granules have no 



relation to the spirochete; (3) that it is impossible to introduce 



them under the skin of animals capable of infection without 



inoculating spirochetes at the same time; (4) spirochetes were 



found in the coelom of all the specimens of Argas j^ersicus 



examined by the authors; (5) these spirochetes were often very 



delicate and w^ere not coloured by the Giemsa stain but were 



brought out by gentian violet ; (6) others still more delicate were 



found which remained almost invisible no matter what the stam 



employed; (7) the authors failed to clear infected specimens of 



Argas from their spirochetes; (8) a large number of spirochetes 



ingested by a specimen of Argas immediately passed through the 



intestinal wall and distributed themselves about the coelom : (9) 



those which remained in the gastric caeca degenerated in 8 to 12 



days: (10) the breaking up of the chromatin in the spirochete 



cannot be considered as a transformation of these organisms into 



granules, but is rather a process of degeneration: (11) Leishman's 



