50 



water containing much carbon dioxide the larvae died from carbon 

 dioxide poisoning and not for lack of oxygen, whereas in water con- 

 taining a normal or a slight amount of carbon dioxide they died of 

 paralysis due to lack of oxygen. Culex larvae can only draw a 

 relatively small quantity of oxygen from the water for use in producing 

 energy. Some other experiments led to the surprising result that 

 instead of gradually emptying during submersion the tracheae fill 

 still more and that when they are quite full small gas bubbles escape 

 from the siphon, which is therefore not always completely closed under 

 "Witer, This gas cannot be oxygen, for asphyxiation could not be 

 passible in the presence of an excess of oxygen. It is possible that 

 the blood provides for the reception and carriage of carbonic acid 

 peDetra,ting from without or produced by changes of the cell-tissues, 

 or that air " that has already been breathed " is stored up in the 

 tracheae. Intestinal respiration does not appear to be involved, but 

 the removal of the branchial leaflets causes a reduction in the capacity 

 to absorb oxygen. The chief function of the branchial leaflets is 

 probably the absorption of oxygen, while (subject to the restrictions 

 mentioned) the elimination of carbonic acid from the blood occurs 

 through the body-walls. 



Grant (J. T.) & Bacot (A.). Experiments concerning the Efficiency 

 of Hot-air Huts for the Disinfestation of Blankets and Clothing, — 

 JL RA.M.C., London, xxxi, no. 6, December 1918, pp. 443-461, 



4 plans. 



The efEects of the exposure of lice and their eggs in hot-air huts, 

 in which the source of heat is coke braziers, fall into two categories, 

 (1) that in which the effects are optically visible with a magnification 

 of about 10 diameters ; (2) that in which there are no immediate 

 visible signs of the cause of death of active lice, and incubation of the 

 eggs is necessary in order to test if they are killed or not. 



The line of demarcation corresponds roughly with 30 minutes' 

 exposure to a temperature below or above 140° F, If above this, 

 the eggs are collapsed or shrivelled and the bodies of the lice are dried 

 up, discoloured or brittle according to the extent of the rise above 

 140° F. If below, the lice are soft, and little, if at all, discoloured, 

 while the appearance of the eggs would be unchanged. An outstanding 

 feature of the effect of heat on the eggs is the very narrow range of 

 its variable action, there being only one instance recorded of partial 

 action, when a temperature of 125° F. killed all but 2 or 3 eggs out of 

 more than 50 exposed. The experiments, which are described in 

 detail, showed that a temperature of 132° F. is amply sufficient to 

 destroy both lice and their eggs, with a minimum of 15 minutes' 

 treatment, even when protected by more than one thickness of khaki 

 cloth ; in this case the door thermometer registered 140° F, throughout 

 the tests. This allows a good margin for faulty construction, but a 

 thoroughly well constructed and efficiently worked hot-chamber ought 

 to be able to run safely at 132° F. Mixed wet and dry garments 

 should not be treated at the same time, as some of the eggs in wet 

 garments might escape destruction, and the moisture would tend 

 to reduce the temperature in the dry ones. Equalisation of the 

 temperature throughout the hut is of great importance, and it is 



