99 



mud ; it kills algae and grasses. The disadvantages are : It does not 

 •emulsify and is inert in brackish water ; it must be kept in closed 

 vessels ; it rapidly loses its toxicity when mixed with water containing 

 algae and other organic matter. 



In a chapter on natural enemies the value of small fish and the 

 limitations of their action are discussed at length; the larvae of 

 dragonflies and water beetles were found to be of great value in 

 places where fish could not live; certain birds, especially night jars, 

 as well as bats, consume large numbers of adult mosquitos. 



The use of screens and the destruction of adult Anophelines in 

 houses are dealt with at length. In Panama only the best copper 

 gauze, made of wire one-hmidredth of an inch in diameter and having 

 18 strands to the inch, can be used ; 18 mesh No. 31, B.W.G. is the 

 technical description of this gauze. Useful hints on construction and 

 fitting and for the adaptation of screening to tents and railway cars 

 are given. Stress is laid upon the fact that defective and damaged 

 screening is worse than none at all. Details of the construction of 

 gauze labyrinth traps, which are said to be very useful, are also given ; 

 these should be attached to the lee side of buildings for Anophehnes 

 and to the windward side for Culicines. This part of the work 

 concludes with a chapter on the results obtained; the accompanying 

 chart, showing the percentage of cases among the employes of the 

 Isthmian Canal Commission from November 1905 to December 1913, 

 demonstrates that scientific warfare against mosquitos has made the 

 €anal Zone habitable and rendered possible the construction of the 

 canal. 



The second portion of the book, comprising 93 pages, is devoted 

 to the campaign in Havana and on the Isthmus against yeUow fever. 

 The importation into the Canal Zone of large numbers of non-immune 

 labourers presented serious possibilities, and every possible measure 

 was and has been taken to protect them from infection. Attention 

 is drawn to the danger of infection by what are known as walking 

 •cases of yellow fever^ — i.e., so slight as not to prevent the sufferer 

 from going about. The opinion is however expressed that the com- 

 plete suppression of Stegomyia is not necessary, though desirable, and 

 that its reduction in a given locality to a point below that required 

 to propagate the disease is sufficient ; what this point should be, 

 must be settled for each separate locality and would vary with the 

 number of cases present. 



This book is an exceedingly clear and well ^^^:itten record of 

 probably the largest sanitary work ever undertaken. The maps and 

 illustrations are well chosen and give a clear idea of the conditions 

 under which the work was carried out and the difficulties to be 

 contended with. The style of the book is such as to be readily 

 comprehensible to the layman, and it is perhaps the best general 

 testimonial to the great importance of Applied Entomology that has 

 appeared for some time. 



