98 



NATURE 



[January 26, 1922 



(3) He built the first internal-combustion motor 

 suitable for a practical man-carrying aeroplane. 



(4) He developed and successfully launched the 

 first gasoline model aeroplane capable of sustained 

 free flight. 



(5) He developed and built the first man-carrying 

 aeroplane capable of sustained free flight. 



Only the last of these items appears to be in dis- 

 pute, and, even were adverse criticism justified, the 

 merit of Langley's work would scarcely be affected. 

 It is not disputed on the other side that the Wright 

 brothers made the first sustained flight and so 

 marked a stage of progress which appealed to the 

 world at large instead of to a limited number of 

 men of science. The list of earlier contributors to 

 progress in aviation is long, and all deserve some 

 credit for the ultimate result, but the modern phase 

 took its beginning with the publication of Langley's 

 researches on aerofoils, etc., and the additional spur 

 given by the successful flights of his power-driven 

 models. 



It is not too much to say that more original and 

 personal solid work underlay the Langley aero- 

 plane than is the case for any other aeroplane, not 

 excepting those of the present day. The solution 

 of the problems of stability which Langley reached 

 as a pioneer in one instance is still beyond the 

 powers of the majority of his successors in the art 

 of aeroplane design. 



Intestinal Protozoa of Man 



The Intestinal Protozoa of Man. By Clifi'ord Dobell 

 and F. W. O'Connor. Pp. xii-f2ii-h8 plates. 

 (London : Published for the Medical Research 

 Council by J. Bale, Sons, and Danielsson, Ltd., 

 1921.) 155. net. 



THIS is a treatise which will be very valuable 

 to the medical investigator of the micro- 

 scopic intestinal parasites of man — other than those 

 belonging to the great group of Bacteria. Its origin 

 is due to the continuous and comprehensive study, 

 made during the great war, of the relation to para- 

 sitic Protozoa of dysenteric disease occurring in 

 the British Army. Mr. Cliff^ord Dobell has previ- 

 ously published various reports of his masterly work 

 on this subject, and two years ago (December 11, 

 1919, vol. 104, p. 369) we noticed in these columns 

 his critical essay entitled " The Amoebse Living in 

 Man." In the present publication Mr. Dobell has 

 been assisted by Mr. F. W. O'Connor, who had 

 independently carried on investigations on intestinal 

 Protozoa in connection with the Egyptian Expedi- 

 tionary Force. Mr. O'Connor was to have been 

 specially responsible for the medical parts of this 

 book, and Mr. Dobell for those parts which are 

 NO. 2726, VOL. 109] 



purely zoological. But, owing to the departure of 

 his medical colleague in 191 9 on an expedition to 

 the Gilbert and Ellice Islands, the task of com- 

 pletion of the work and responsibility for the greater 

 part of it have fallen on Mr. Dobell. The treatise 

 is distinguished by that patient inquiry into pre- 

 vious work and critical judgment as to nomenclature 

 and synonomy which have rendered Mr. Dobell 's 

 earlier publications of special value. It is abso- 

 lutely necessary that medical men and proto- 

 zoologists should 'agree upon a terminology in order 

 that they may understand each other's writings, and 

 this result Mr. Dobell 's careful review and original 

 observations enable them to achieve. 



The book is divided into nine chapters, followed 

 by a very complete bibliography and an index and 

 eight plates. Chap, i is an introduction to the 

 whole subject, and is followed by chap. 2 on 

 the intestinal Amoebge of man; chap. 3,. 

 Amoebiasis (the name given to infection by 

 Amcebse, and especially by A. histolytica) ; chap. 4, 

 the intestinal Flagellates of man; chap. 5, the 

 intestinal Coccidia of man; chap. 6, the intestinal 

 Ciliates of man; chap. 7, the diagnosis of intestinal 

 protozoal infections ; chap. 8, the treatment of in- 

 testinal protozoal infections; and chap. 9, the copro- 

 zoic Protozoa of human ffieces. 



One of the chief sources of error which has to 

 be guarded against by the novice in this study is 

 that of supposing that parasites found "in the faeces 

 are necessarily parasites of the intestine. There is 

 a whole series of Amoeba-like and flagellate Protozoa 

 which are present in the soil and may obtain access 

 to, and develop in, the faeces after deposition. 

 These are called " coprozoic Protozoa." They may 

 also obtain access to the faeces by means of resistent 

 spores which are swallowed with dust and pass un- 

 injured and undeveloped into the intestinal contents. 

 Apparently the high temperature of the intestine is 

 unfavourable to their development, which occurs 

 only when they have passed to the cooler conditions 

 of the outer world. Many mistaken descriptions 

 of protozoal parasites have been due to this source 

 of error. 



The Protozoa which are not merely coprozoic, but 

 actually live in the intestine of man, are only seven- 

 teen in number — viz. five AmoebEe, five Flagellata,. 

 four Coccidia, and three Ciliata. Some of these 

 are very rare or exceptional ; others are abundant, 

 but are not shown to be harmful. Only two which 

 actually sometimes (but not always) destroy the 

 tissue of the intestinalwall or of other organs when 

 present in man are admitted by Mr. Dobell to be 

 pathogenic — viz. Entamoeba histolytica and the 

 ciliate Balatttidium coli. The work of recent years, 

 and much of that of Messrs. Dobell and O'Connor, 



