Hi 



NATURE 



[April 13, -1916 



species of mosquito concerned, the result of the 

 draining- on the breeding-places, and generally a 

 fuller account, but perhaps these will be found in 

 another work to which the author refers, and here 

 only the broad outline was intended. 



The author in writing- is inclined to use rather 

 vague expressions, such as " a long series of blood 

 examinations " (the number is not given), " proved 

 up to the hilt " (sometimes a very dangerous ex- 

 pression, as one could easily show), "quinine in 

 every shape and form " (dose not stated), " a high 

 percentage " of the labourers harbours malaria 

 parasites (figure not g-iven), and his use of figures 

 is not entirely satisfactory, e.g., in the Panama 

 chapters he quotes figures to show that there were 

 eighty-three cases of haemoglobinuric fever among 

 •Barbados natives, while there was only one 



author is the " flights of mosquitoes *' noted in the 

 Canal zone. 



These began about 6 p.m. and ceased before 

 9 p.m. " Hundreds of Anopheles could be seen 

 passing by," and the flights attracted insecti- 

 vorous birds to activity. The range of flight was 

 about 6000 feet, originating- in a marsh and ter- 

 minating in an inhabited area, the object of the 

 flight being apparently blood. 



A most important fact that the author draws 

 especial attention to is that in certain estates in 

 British Guiana malaria has disappeared. Agricul- 

 ture has in some way, for all practical purposes, 

 abolished it. Anopheles do not breed in the water 

 in land which is cultivated in British Guiana, but 

 Culex do so in abundance. Now a knowledge of 

 what exactly is implied in the term " agriculture "" 



II 



Land raised by " hydraulic filling" on the east bank of the French canal at Gatun. The remains of the swamp trecb are still to be seen. 



From " Rural Sanitation in the Tropics." 



among natives of Costa Rica ; but as no data are 

 supplie?l as to the relative number of these two 

 classes of labourers, one can draw no valid con- 

 clusion. On pag-e 249 the admission rate in 1906 

 for malaria among a labour force of 26,705 was 

 821 ; in 191 3 the rate for a force of 56,654 was 

 76. Now in order that these figures should be 

 comparable it should have been shown that the 

 percentage composition of the force as regards 

 races was the same in 1913 as it was in 1906, but 

 this is not done. One has little doubt that there 

 has been this fall, but the figures per se do not 

 completely prove it ; if, for instance, the white 

 population had been partly replaced by the rela- 

 tively immune negro In the interv^al, this would 

 vitiate the figures. 



A very interesting phenomenon recorded by the 



NO. 2424, VOL. 97] 



here is of the first importance. We should| 

 imagine no more valuable data could be givCBi 

 than would be in an account of the difference 

 between a malarial area and a non-malarial area 

 in British Guiana. This book should be read by 

 all officials who obstruct, or turn a deaf ear to, 

 the claims of sanitation, though there are other 

 necessities of life, as the author points out in 

 his epilogue. J. ^^^ W. S. 





THE POLLINATION OF FRUIT TREES. 

 INVESTIGATIONS carried out in this country., 

 J- in America, and elsewhere have demonstrated 

 the fact that many of our cultivated varieties of 

 apple, pear, plum, &c., are self-sterile. They' 

 have shown, moreover, that whereas a variety 



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