April 7, 192 1] 



NATURE 



167 



our opinion, could have been omitted with no great 

 loss, especially in a volume of this nature. 



In some sections, on the other hand, the con- 

 ciseness has been rather overdone. The chapter 

 on muscle is somewhat condensed, especially the 

 paragraph dealing with visceral muscle, which, 

 as in many other text-books, is quite over- 

 shadowed by the record of experiments on the 

 gastrocnemius of the frog. The paragraph on the 

 reaction of the blood, containing, as it does, an 

 explanation of hydrogen-ion concentration, could 

 have been longer and clearer. This subject is 

 usually a very difficult one for the average 

 student, and requires a good deal of explanation. 

 It would have been wise to devote a full 

 paragraph to a description of what hydrogen-ion 

 concentration means, especially as this term is 

 coming into greater use every day. 



The section on the gases of the blood is very 

 full, and contains an account of all the recent 

 work. Barcroft's differential apparatus is figured 

 and explained. A very good feature of the book is 

 the illustration of the text with representative 

 tracings. This, we think, is very important for 

 the proper understanding of a subject like physio- 

 logy, which is, and always must be, practical. 

 The presence of these typical tracings saves the 

 reader from- cramming facts, an obvious danger 

 in such a concise book. 



The chapter on the ductless glands is well 

 illustrated by photographs of typical cases show- 

 ing the effects of withdrawal of the various 

 secretions. This is of advantage, as it impresses 

 on the student the close relationship between 

 physiology and the actual practice of medicine. 

 The chapter makes mention of most of the recent 

 important work in endocrinology — e.g. there is 

 noticed the work of the Glasgow school under 

 Prof. Noel Paton in connection with the para- 

 thyroids and guanidin. 



On the whole, the book ought to prove useful 

 for students going up for their second profes- 

 sional examination, after they have gone through 

 the necessary practical classes. 



Our Bookshelf. 



Applications de la Photographie Airienne. By 

 L.-P. Clerc. (Encyclopedic Scientifique.) 

 Pp. vi-i-35o-)-xii-hx plates. (Paris : O. Doin et 

 Fils, 1920.) 7.50 francs. 



In the production of aerial photographs the results 

 of diverse scientific investigators have been used, 

 but even when the ideal photograph has been 

 obtained, its value is small without a knowledge 

 of its geometrical properties and of the methods 

 by which it can be most fully employed. The 



NO. 2684, VOL. 107] 



present work deals mainly with the geometrical 

 problems which form the foundation of the use 

 of air-photographs for precise work, and it is the 

 element of precision which makes the aerial pic- 

 ture so valuable. The book is divided into three 

 parts. The first treats briefly of interpretation, 

 and includes the calculation of the heights of 

 objects from their shadows. The second part 

 deals with stereoscopy, and is of great value. It 

 covers the groundwork of the subject very fully, 

 and will be invaluable in working out metrical 

 methods in practice. The third part deals with 

 metrophotography, and contains many of the re- 

 sults discovered by earlier workers in photo-sur- 

 veys from balloons, together with new work. The 

 general treatment suggests that the author has 

 been more occupied with the theory of the air- 

 photograph than with the results obtained in prac- 

 tice, and in his introduction he refers rather bit- 

 terly to the photographic organisation of the 

 French Services. Whatever may have been the 

 situation during the war, M. Clerc must have the 

 satisfaction of knowing that his unique work will 

 greatly assist the future development of scientific 

 air-photography. H. H. T. 



Essays on Early Ornithology and Kindred 

 Subjects. By J. R. McClymont. Pp. vii-h35 

 + 3 plates. (London: Bernard Quaritch, Ltd., 

 1920.) 65. 



The author has been diving in the rather muddy 

 waters of early ornithology, and displays some of 

 his treasures in a beautifully printed book. 

 Marco Polo's rukh holds a position in bird-lore 

 intermediate between the utterly fanciful and the 

 badly misinterpreted, say between the Phoenix and 

 the apodous Birds of Paradise. A mythological 

 stream, taking its rise from the simourgh of the 

 Persians, and a matter-of-fact stream, taking its 

 rise from observations on some sea-eagle, united 

 into one, which " floated the conception of the 

 rukh." An anonymous narrative of the first 

 voyage (1497) of Vasco da Gama to India contains 

 a reference to the penguins and seals of what 

 is now called Mossel Bay. A hundred years after- 

 wards a scurvy-stricken ship found in an island 

 in the bay ' ' many birds called Pyncuins and Sea 

 Wolves, that are taken with men's hands " (the 

 baby Otaria pusilla?). The third study deals 

 with the birds of the Banda Islands, where 

 nutmeg-trees flourish; the fourth discusses the 

 etymology of the name " Emu," the suggestion 

 being that the Portuguese changed the Arabic 

 name of the cassowary, " Neama," into " uma 

 ema. " The identification of Australian birds 

 mentioned by Dutch explorers in 1697 and of New 

 Zealand birds observed by Crozet in 1772 has 

 all the fascination of a clever game. Mr. 

 McClymont 's studies are what we should call 

 luxuries, but they have the merit of scholarship 

 and brevity. There are three fine plates, show- 

 ing Casuarius uniappendiculatus, Blyth {juv.), 

 from the British Museum; Hulsius's figure of an 

 " Erne," an immature cassowary with two 



