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Alessandrtni (G.). I Pidocchi nella Profllassi del Tifo esantematico. 



[Lice in Connection with the Prophylaxis of Exanthematous 

 Tj'phus.] — Ann. (TLjieae, Rome, xxix, no. 9, 30th September 

 1919, pp. 557-598, 9 figs., 8 plates. [Eeceived 30th December 

 1919.] 



In the case of Haematopinas suis and in Pediculus humanus fed on 

 pigs the author states that 80 per cent, of the larvae yield females. 

 Assuming the number of eggs per female to be 70, the third-generation 

 progeny of one pair of lice may number 44,689 males and 178,751 

 females. With regard to the resistance of lice to fasting, larvae that 

 have not yet moulted cannot live more than 30 hours without food ; 

 after 10-12 hours they become inactive and though they may attempt 

 to feed again after 20-25 hours they do not recover. Larvae that have 

 moulted behave similarly if prevented from feeding immediately 

 after moulting, but if allowed even one feed their resistance is increased ; 

 some remained alive for 3 days at 82° F. (28° C.) Besides this capacity 

 for fasting and resisting unfavourable temperatures lice possess in 

 their organs of touch, smell and sight important means of defence 

 against such conditions. Tactile sensibility depends chiefly on 

 a perception of varying degrees of heat. The author uses this fact 

 when collecting lice. Infested rags and other materials are put 

 in a glass funnel placed on a thermostat with its nozzle inside the 

 chamber. The chamber is heated to the optimum temperature and 

 the lice soon leave the rags and sliding down the nozzle fall into a 

 dish below. The sense of smell jjlays the most important part in 

 keeping lice from unsuitable situations. Agricultural labourers with 

 habits of personal uncleanliness similar to those of beggars are stated 

 to remain uninfested because, whereas the beggars have a " human " 

 odour, the labourers dispense an earthy smell with an aroma of garlic 

 and onion due to their diet. The influence of light is well Icnown and 

 also that exercised by colour. In view of the above facts it is clear 

 that migrations of these parasites are mainly due to their own activity ; 

 passive carriage by other insects or wind may occur, but only 

 exceptionally. 



In a previous paper [R.A.E., B, iv, 83] various remedial measures 

 were discussed. Since then many new suggestions have been 

 advanced, but it still remains true that very few methods are quite 

 reliable and some of them have no practical value. Exposure to 

 dry heat or to sulphurous anhydride appear to be the best measures 

 hitherto discovered. The author's method of using sulphurous 

 anhydride is as follows : The garments to be treated are placed in 

 a wooden or earthen container in which a given quantity of a 4 per 

 cent, solution of commercial sulphuric acid has been placed. When 

 the clothes have been stirred about and well soaked, a 20 per cent, 

 solution of sodium hyposulphite, double the quantity of the former 

 solution, is added. The clothes are again thoroughly stirred and 

 a very close-fitting or hermetically-sealed lid is put on. Pediculus 

 humanus (vestimenti) and Haematopmus suis die after submersion for 

 10 minutes, even if the clothes are rinsed with plain water immediately 

 afterwards. The eggs of these lice are kiUed at the same time. Even 

 when protected by bags of material of varying thickness the Hce and 

 their eggs die in 10 minutes, or in 20 minutes if the material is the 



