172 



NATURE 



[June 25, 1903 



Filaria Persians as the causative agent of sleeping 

 sickness (p. 408). This view had prevailed in the text- 

 books for some time, but the Royal Society's commis- 

 sion has shown at once that the facts will not support 

 this view. These then are instances where a personal 

 acquaintance of even a few months' duration of 

 the disease under consideration has considerably 

 modified received opinions. But we cannot always 

 hope to have critical inquiries of this kind by trained 

 observers. We are, unfortunately, left with the second 

 much inferior method, viz. the diligent searching out 

 of all that has been written on the diseases in question, 

 more especially in the latest periodical literature. Here 

 we are immediately confronted with the difficulty of 

 knowing what to believe amidst the mass of published 

 articles, and when we see some of the sources from 

 which the author has only too frequently quoted, we 

 consider that he has not had a due appreciation of the 

 extremely untrustworthy nature of much of his 

 material. 



With this qualification then, viz. a too ready willing- 

 ness to admit the statements of uncritical writers, we 

 can only find praise for the large mass of material con- 

 densed by the author. To hope to find any general ex- 

 planation of the distribution of diseases is, we think, at 

 present premature. We may point out finally some 

 details of particular diseases where the information is 

 inadequate or inaccurately set forth. On p. 237, the 

 principal carrier of malaria is said to be A. Claviger. 

 This is a curious statement, seeing that it does not 

 occur in tropical Africa, India, Malaysia, &c. Possibly 

 the author had Europe alone in his mind. Nor should 

 we think that Grassi holds that any species of Culex 

 can transmit malaria. The malaria of cattle is quite 

 a different disease from that of man, and it is not 

 accurate to use this term in reference to pyroplasma 

 bovis (p. 243). Again, the malarial statistics of India 

 have been, up to the present, so notoriously untrust- 

 worthy that we doubt much the value of quoting state- 

 ments about " an increased production of the poison " 

 in famine years (p. 248). Nor is it true that the 

 Central Provinces are among the most malarious 

 territorial divisions of India. 



Turning now to that peculiar manifestation of 

 malaria, blackwater fever (p. 44), we note the omission 

 of Palestine as an important focus of this disease. So 

 virulent is it there among the Jews that some villages 

 have been deserted. On p. 51 the author writes, 

 " whether haemoglobinuric fever in man is due to the 

 same organism as the red water fever of cattle is 

 uncertain." In our opinion it is absolutely certain 

 that it is not, for the simple reason that this organism 

 (pyroplasma) of cattle has a characteristic and easily 

 recognised appearance, and exists in abundance in the 

 blood and organs, but has never been seen or described 

 by anybody in the blood or organs of blackwater 

 patients. The recent commission on malaria appointed 

 by the Royal Society has likewise shown that in the 

 Duars (India) it is as common as in tropical Africa. 

 Nor do we consider that an abundance of observations 

 has been published tending to disprove Koch's views 

 of blackwater; on the contrary^ the Royal Society's 

 NO. 1756, VOL. 68] - 



commission was of precisely the same view as 

 Koch. 



Sprue (p. 127) undoubtedly exists in India, as a 

 typical case from there in a lady came recently within 

 our knowledge. It is quite certain, however, that the 

 aetiology and differentiation of hill-diarrhceas in 

 India is completely obscure at present. We have 

 already referred to the work of the sleeping sickness 

 commission, but it seems probable that when its com- 

 plete reports are published our knowledge of the dis- 

 tribution of Filaria will be considerably modified. 



While we have pointed out in what respect we con- 

 sider this book deficient, yet it must not be thought 

 that we have not a full appreciation for the industry 

 which it must have necessitated ; and those students 

 who wish to possess a well-arranged book of reference 

 on the distribution of diseases ought to be exceedingly 

 grateful to the author, but when consulting it they 

 should remember that the subject is hardly yet capable 

 of accurate treatment. J. W. W. S. 



HYDRODYNAMICAL FIELDS OF FORCE. 



Vorlesungen uber hydrodynamische Fernkrafte nach 

 C. A. Bjerknes' Theorie. Von V. Bjerknes. Band 

 ii. Pp. xvi + 316. (Leipzig: Johann Ambrosius 

 Barth, 1902.) Price 10 marks, or 11.50 marks bound. 



THE first volume of this book, which was reviewed 

 in Nature for November 3, 1900, is of a theoret- 

 ical character, and deals with the stream lines in a per- 

 fect liquid considered especially with reference to the 

 motions set up by moving solids and in particular pul- 

 sating, oscillating, or moving spheres. In it were ob- 

 tained results now well known to students of hydro- 

 dynamics showing the existence of attractions and re- 

 pulsions between the spheres, bearing a considerable 

 analogy to the forces occurring in gravitation and other 

 physical phenomena. 



The interest of these results is greatly enhanced by 

 the experiments described in the present volume. These 

 experiments were commenced in the summer of 1875 

 by the late Prof. C. A. Bjerknes, who observed that if 

 two spheres lighter than water (croquet-balls were used 

 in the first instance) are allowed to fall into a tank of 

 water from the same height, so as to set up vertical 

 oscillations at the surface, they will approach each 

 other if let fall simultaneously, and will recede from 

 each other if let fall so that their oscillations are oppo- 

 site in phase. From the fact that the volumes dis- 

 placed by the spheres vary, the conditions are in many 

 ways analogous to those produced in an infinite liquid 

 by " pulsating " rather than oscillating spheres. 

 From this beginning more elaborate experiments were 

 devised. A sphere falling in liquid in the neighbour- 

 hood of a vertical wall in which its image could be 

 seen by reflection was found to reproduce the attrac- 

 tions and repulsions indicated by theory for a pair. Of 

 spheres moving symmetrically. The next experiments 

 were conducted with spheres so fixed as to perform 

 pendulum oscillations below the surface. The experi- 

 ments were first performed at home, but from 1876 to 

 1880 Prof. Schiotz arranged for their continuation in 



