Geeen (H. H.). Description of a Bacterium, isolated from a Cattle 

 Dipping Tank, which reduces Arsenate to Arsenite. ■Union, S. 

 Africa Dept. Agric, 5th and 6th Repts. Direc. Vet. Research, April 

 1918, Pretoria, 1919, pp. 611-624. [Received 13th November 

 1919.] 



An organism that rapidly reduces sodium arsenate to sodium 

 arsenite, and the source of which is probably faecal, has been isolated 

 from an arsenical dipping tank. It is provisionally named Bacterium 

 arsenrediicens, and counteracts the oxidation brought about by 

 B. arsenoxydans [see preceding paper]. While anaerobic conditions 

 reduce the activity of this organism, free aeration accelerates its 

 growth, and in suitable media, complete reduction of 0'2 per .cent, 

 arsenate can occur in 48 hours in any depth of layer. In mixed 

 cultures containing the oxidising organism either arsenate or arsenite 

 can be produced at will by varying the composition of the medium. 

 Upon addition of glycerine, ghicose, or fresh stable manure, the 

 reducing organism out-numbers the oxidising organism and reduction 

 occurs. 



The significance of this in relation to dipping tanks in the field is 

 discussed. The organism is non-pathogenic for rabbits and guinea- 

 pigs, and probably also for man. 



Bedford (0. A. H.). Notes on the Species of Gastrophilus found in 

 South Africa. — Union S. Africa Dept. Agric, 5th and 6th Re2)ts. 

 Direc. Vet. Research, April 1918, Pretoria, 1919, pp. 627-642, 

 17 figs. [Received 13th November 1919.] 



Of the three species of Gastrophilus found parasitic upon horses, 

 mules and donkeys in South Africa, G. intestinalis, DeG. {eqid, Clark) 

 is the commonest ; G. pecoruni, F., and G. nasalis, L., also occur 

 abundantly, probably on account of the dryness of the climate. The 

 only other Oestrid that has been found parasitic upon horses in South 

 Africa is a nasal fly, probably belonging to the genus Rhinoestrus, 

 and this is very rare. In ex-German East Africa and in the Sudan 

 G. asininus, Brauer, has been recorded, but this is probably only a 

 variety of G. intestinalis. Tables are given distinguishing these 

 species both in the adult and larval forme, and descriptions are given 

 of the stages and life-histories of the three S. African species. These 

 keys include G. hacmorrhoidalis, L., which has not at present been 

 found in South Africa, but is Uable to be imported at any time in 

 horses from Europe or America. 



G. intestinalis is found in the stomach of practically all horses 

 examined after death, and in many donkeys and mules. Dogs are 

 occasionally infested, but this is probably not a normal occurrence 

 as it is doubtful whether these larvae can live for any length of time 

 in the stomach of a carnivorous animal. In such cases the larvae 

 are probably ingested with horse dropping-. The egg-stage of this 

 species is apparently from 7 to 13 days, which is a shorter period than 

 that required in North America. The adults are abundant from 

 February to April. 



G. pecorum was very common at Onderstepoort in 1913 and again 

 in 1916 during the same season. The larvae occur in the stomach, 

 pharynx, and oesophagus of horses. The adults appear from February 



