REVIEWS 723 



much that he has to say concerning the coco-nut applicable to the warfare against 

 plant-disease in tropical agriculture generally. He points out, for instance, that 

 whereas in the temperate regions the spread of pests is checked by winter, 

 and there occur extensive forest formations made up of one or a few species, in 

 the tropics the climatic conditions controlling plant communities and the climatic 

 opportunities for epidemics make it impossible for such pure formations to exist in 

 nature ; hence, if men will plant and maintain forests of coco-nuts, or any other 

 single tree in the tropics, it will prove possible only by much greater precautions 

 against disease than are required by any crop of temperate lands. 



In the remaining chapters the author deals with the selection and treatment of 

 seed, field culture, and coco-nut products. Throughout he calls attention to points 

 which require investigation, but have hitherto received little or no attention 

 despite their importance. For instance, he emphasises the need for detailed and 

 systematic experiments in the breeding of coco-nuts. While acknowledging the 

 valuable work done in Madagascar under the auspices of the French Ministry of 

 Colonies in the study of varieties, races, and strains, he points out that at present 

 nothing is known as to thoroughly distinct varieties that can be trusted to breed 

 true, or as to the suitability of different varieties for different climatic or soil 

 conditions. 



F. Cavers. 

 APPLIED PHYSIOLOGY 



Report of the Committee on Standards and Methods of Examining the 

 Color Vision. Reprinted from the Transactions of the Section on 

 Ophthalmology of the American Medical Association. Chicago, June 

 1914. 

 The Committee commences its report with a theoretical exposition and classifica- 

 tion of colour-blindness on a modified form of the trichromatic theory. It is 

 curious that so many committees appointed for a practical object adopt a 

 theoretical basis which, in the case of the trichromatic theory, is different in 

 each case, and quite irreconcilable with each other or with the true facts of 

 colour-blindness. 



The Committee give a detailed account of the methods in use in foreign 

 countries. This is very complete and well done, and contains much valuable 

 information. An error, however, is made in stating that the British Admiralty use 

 Holmgren's test in addition to Edridge-Green's lantern and spectrometer. The 

 British Admiralty only use Edridge-Green's methods. 



The final section deals with the methods in use in the United States, Canada, 

 and the Public Health Service. Twenty-five railroads use a lantern in all cases, 

 six railroads use a lantern in special cases, twenty-one railroads do not use 

 a lantern in any case. The lantern used in these cases must be of a very defective 

 character, as an examination of the replies of the examiners shows that very few 

 of those rejected by the lantern failed to be detected by the very inefficient wool 

 test. As is well known, over 50 per cent, of dangerously colour-blind persons 

 rejected by Edridge-Green's lantern will pass the wool test, even in its most 

 approved form, with the ease and accuracy of a normal-sighted person. The 

 Committee has not recognised that a dangerous dichromic or trichromic can pass 

 the wool test with ease. It has, however, recommended that a lantern test should 

 be used in all cases in addition to the wool test, in order to detect (1) those with a 

 shortening of the red end of the spectrum, and (2) those with a central scotoma 

 for red and green. 



It is to be hoped that the next Committee appointed on colour vision will base 



