18 



10 days at winter temperatures, 0°-10° C. (32°-50°F.). As it is not 

 always possible to distinguish strictly between these seasonal tem- 

 peratures, the maximum period of 10 days must be used in practice. 

 The female may be considered capable of oviposition at a temperature 

 as low as 15° C. (59° F.), indicating that at winter temperatures ovi- 

 position ceases, though the lice are able to live longer, whereas they die 

 quicker at summer temperatures, but are able to breed. It may lead 

 to error if temperatures are considered when calculating the number 

 of days during which a starving female is able to oviposit, and for this 

 reason the time was taken after which no eggs are laid, even at 

 favourable temperatures. This time is 5 full days without any food. 

 Eggs do not hatch at a constant low temperature of 20° C. 

 (68° F.) ; at a constant temperature of 25° C. (77° F.) incubation 

 requires 16 days. At a constant temperature below the requisite 

 minimum, development ceases and hatching is delayed. In his 

 experiments the author was able to delay hatching for 11 days by 

 a daily change from a warm to a cool temperature, the latter varying 

 from 10°-12° C. (50°-54° F.), a condition quite common at night and 

 represented in practice by the laying aside of infested clothing at that 

 time. In another experiment the daily change of temperature was 

 replaced by an alternation of a series of warm and cold days, and it 

 was found that the eggs resist without injury a series of 5 successive 

 cold days at any point of their developmental period. A test was made 

 to ascertain how long newly hatched larvae can resist starvation, and 

 this period was found to be 5 days at a room temperature of 15°-20° C. 

 (59°-68° F.) ; at 10°-12° C. (50°-54° F.) this was prolonged to 7 days. 

 The above results lead to the conclusion that a period of 39 days 

 (5 + 16-fll+7) is necessary in practice if the starvation method of 

 killing lice is to be depended upon in order to render clothes, household 

 and other articles free from them. 



Werner (H.). Zur Aetiologie der Febris quintana. [On the Aetiology 

 of Five-Day Fever.] — Centralbl. Bakt., Parasit. u. Infektionskr., 

 Jena, Ite Abt., Orig., Ixxxii, no. 7, 25th March 1919, pp. 571-576, 

 2 figs. [Received 17th November 1920.] 



The transmission of five-day fever from man to man may occur 

 through infected blood or through the bites of lice. This proves that 

 the virus circulates in the blood and is taken up by the louse. It is 

 not certain whether development occurs in the louse or whether trans- 

 mission is purely mechanical ; the latter is probable. As regards the 

 various supposed causal agents, it is not improbable that Rickettsia is 

 connected with the disease, but this is uncertain. 



Prell (H.). Ueber eine enzystierte Fliegenlarve aus der Leibeshohle 

 des Grasfrosches. [An encysted Fly Larva from the Body-Cavity 

 of the Grass Frog.] — Centralbl. Bakt., Parasit. u. Infektionskr., Jena, 

 Ite Abt., Orig., Ixxxiii, no. 7, 31st October 1919, pp. 541-549, 

 5 figs. [Received 17th November 1920.] 



Details are given regarding the presence of a fly maggot in a cyst 

 in a grass frog captured near Stuttgart, though this parasitism is 

 beheved to be quite accidental. 



