374 MOSQUITOES OF NORTH AMERICA 



mosquitoes, and that it is quite as efficacious when dry as when moist. He 

 shows that it has surprising power of penetrating through clothing and fabrics, 

 and that it will kill mosquitoes even when hidden under four layers of toweling 

 in one hour's time and with very dilute proportions. He states that although 

 this substance has long been disparaged as a disinfectant because it fails to kill 

 spores, it must now be considered as holding the first rank in disinfection 

 against yellow fever, malaria, filariasis, and other insect-borne diseases. 



MERCURIC CHLORIDE. 



In the Public Health Eeports, volume 24, No. 50, December 10, 1909, 

 pp. 1859-1861, Surgeon G. M. Guiteras, U. S. Public Health and Marine-Hos- 

 pital Service, has recounted a series of experiments with this substance, the use 

 of which was first suggested to him by G. F. Matzke, steward on the American 

 steamer " Beecham," who told Doctor Guiteras that he had used it in the cabin 

 of his vessel with success. Doctor Guiteras carried out a series of five experi- 

 ments in a room 12 feet high by 15 feet by 13^ feet, having a capacity of 2385 

 cubic feet, sublimating the mercuric chloride in a porcelain evaporating dish 

 over an alcohol lamp. Mosquitoes in cages approximately containing a cubic 

 foot of space, covered with wire gauze, were exposed at varying elevations in 

 the room, and from 30 to 60 grams of mercuric chloride were sublimated at ex- 

 posures varying from two to three hours, at temperatures of from 77 to 88 

 degrees. Mosquitoes in the upper part of the room were invariably killed, while 

 some of those very near the floor escaped, most of the latter however being killed, 

 and the remainder never recovering perfectly, except in one experiment where 

 the temperature was only 77° F. Twenty-five grams of mercuric chloride were 

 found to be sufficient for 1000 cubic feet of space. He showed that about 20 

 minutes are consumed in sublimating 60 grams of the chloride ; that brass work 

 is not tarnished, and that nickel-plated work and instruments are not tarnished 

 when wiped off immediately after fumigation. He further showed that painted 

 surfaces are unaffected unless the chloride is sublimated close to them and they 

 are not immediately wiped off. Moreover it does not affect colored silk, cotton 

 or woolen goods. The poisonous qualities of the substance, in Guiteras's opinion, 

 do not constitute a real danger. When the room was opened after the experi- 

 ments, he found it filled with a thick mist, but the room was entered without 

 any especial precaution and the windows were opened. In a few minutes the 

 vapor was carried away, leaving a slight deposit on the surfaces within the room. 

 This was allowed to remain for two or three days, and the room was used in 

 the meantime without any bad results. The deposit, however, should have been 

 removed with a damp cloth, and Avith this ordinary care, the experimenter be- 

 lieves, there will be no danger in the use of the substance. 



The advantages he considers to be, the facility of obtaining mercuric chloride, 

 the small quantity necessary, and the simplicity of its use ; a good alcohol lamp 

 and a porcelain evaporating dish constitute all the macliinery necessary, and its 

 use is certainly much more convenient than sulphur where the operators have to 



