March 6, 1902J 



NA TURE 



411 



suppose that the reaction only takes place when the 

 special salt mentioned in the book is used, and if any 

 other salt of the metal is offered to them to say, "but 

 the book says such and such a salt is to be used." On 

 the other hand, when the equations are expressed in the 

 ionic form, as above, the student is perhaps inclined to 

 forget that the anion of the metal and the cation of the 

 reagent also interact. 



There are those who look upon the " ionisation theory " 

 as absolutely false and will have none of it. Others, 

 mistaking theory for fact, ridicule all other theories and 

 dogmatically state that all difficulties are surmounted 

 when approached by means of the ionic theory. There 

 are many, however, who, without subscribing to the 

 opinions of the e.Ktremists, recognise in the ionic theory 

 an extremely useful working hypothesis. Chemical 

 analysis, which is apt to be dry and dull when viewed in 

 — dare we say — the old-fashioned manner, becomes not 

 only interesting, but many of the reactions which were 

 obscure become clear in the light of the ionic theory. 

 Thus, is the action of caustic alkalis upon ferric ferro- 

 cyanide (Prussian blue) always clear to students of the 

 old regime ? They are told that caustic alkalis decom- 

 pose the compound according to the following equa- 

 tion : — • 



Fe,(CN),8-(-i2KOH = 4Fe(OH)3-f3K4Fe(CN)s; 



but this does not explain why the whole of the iron is not 

 precipitated as ferric hydrate. Now according to the 

 ionic theory, this would be explained by saying that 

 Prussian blue is dissociated into the cations 4Fe"' and 

 the complex anions 3Fe(CN)/"' and that only the iron 

 present as the cation is acted upon by the OH' of the 

 potassium hydrate. 



The arrangement of the book before us is in some 

 respects peculiar. The student is first instructed how to 

 construct a wash-bottle. This is followed on p. 3 by the 

 preparation of hydrogen. The preparation of oxygen 

 comes after that of hydrochloric acid and sulphuretted 

 hydrogen, and is followed in succession by the methods 

 of preparation of chlorine, sulphur dioxide, carbon 

 dioxide and ammonia. 



The analytical portion covers the usual ground and 

 contains the usual reactions. Some portions of the 

 chapter on "theoretical foundations" are far from clear, 

 and we very much question whether the average reader 

 will readily understand the two and a half pages on 

 hydrolysis. 



In a pocket at the end of the book there is a rather in- 

 genious blank draught-board with the cations arranged 

 along the top and the anions down the side. The com- 

 pounds formed by the various ions are to be indicated in 

 their proper squares, and if they are precipitates they 

 may be indicated by shading or by filling- in with coloured 

 chalks. 



The book has a table of contents, but no index. Even 

 if the German edition was not indexed, surely the trans- 

 lator might have supplied one. 



By the way, would it not be well if English writers of 

 chemistry books would arrange always to write the posi- 

 tively charged ion in the same way ? As it is, we find it 

 sometimes spelt cation and sometimes kation. 



F. M. P. 

 NO. 1688, VOL. 65] 



THE MOVEMENTS OF THE FOOT AND 



WRIST. 



Der Gang des Menschen. iv. Thiel. Ueber die Bewegung 



des Fttsses iind die aiif deiiselben eiiiwirkenden Krdfte. 



Von Otto Fischer. Pp. 86 ; 3 plates. (Leipzig : 



Teubner, 1901.) Price Mk. 5"5o. 

 Ueber die Bexvegungen in den Ha?idgelenken. Von 



Rudolf Fick. Pp. 54 ; with 8 figures in text and 10 



plates. (Leipzig : Teubner, 1901.) Price Mk. 6'50. 



IT is strange that two men, working side by side within 

 the same university, publishing results of investiga- 

 tions on similar subjects in consecutive pages of the 

 Proceedings of the same learned society, should produce 

 two treatises so diverse in nature as those of Dr. Otto 

 Fischer and Prof. Fick. Each employs a peculiar and 

 comparatively new method for the solution of problems 

 which have been thumbmarked by ten generations of 

 anatomists. Dr. Fischer is a mathematician as well as 

 an anatomist, a combination so rare that, in applying 

 the later methods of mathematical physics to the elucida- 

 tion of the movements of the human body in walking, he 

 has left his colleagues far behind and is almost without 

 audience or critic. Prof. Fick's paper is the result of the 

 application of Rbntgen rays to the study of the complex 

 movements of the wrist-joint, a method only compara- 

 tively new. 



If these authors differ in the methods they have em- 

 ployed they are alike in this, that they are minute, pains- 

 taking and accurate, investigating fully every fact for its 

 own sake, with no thought whatsoever as to its utility. 

 Prof. Fick has determined in millimetres the extent and 

 direction of the movements undergone by each of the 

 nine carpal bones during flexion, extension, abduction 

 and adduction of the wrist. In the last paragraph of his 

 paper he sums up his main result as follows : — 



" In conclusion I would once more emphasise, what 

 this research has again demonstrated, that the mid-carpal 

 joint is indeed no paltry minor articulation (Kein un- 

 wichtiges Nebengelenk) deserving the stepmotherly con- 

 sideration (stiefmiitterliche Berucksichtung) extended to 

 it by most practitioners, but that, for many movements of 

 the hand, it is emphatically the chief joint." 



In this conclusion the author, as he himself explicitly 

 states, only verifies the observation made many years ago 

 by Henke. The elaborate and expensive plates, the type 

 and style in which Prof. Fick's work has been published, 

 make an English anatomist envy the wealth of a German 

 society that is able to devote so much of its funds to the 

 elucidation of so small a part of the human body. 



In his last contribution to the Kinematics of the human 

 gait, Dr. Fischer dealt with the movements of the lower 

 extremity during the cycle of a double stride ; in this, his 

 fourth contribution, he considers the movements of the 

 foot during a corresponding period. The foot is dealt 

 with as if it were detached from and independent of the 

 rest of the body. The forces which act on it during the 

 cycle of a double stride are traced to four sources, viz 

 the muscles (extensor and flexors of the foot), weight of 

 the body, weight of the foot and reaction of the ground. 

 The points at which these forces are applied and the 

 centre of gravity of the foot are determined and diagram- 

 matically represented. The velocity and acceleration of the 



