April 19, 1900] 



NATURE 



587 



widespread the distribution of glycogen is, and we may 

 safely draw the conclusion that its function is extremely 

 important. 



As before, however, we hesitate to follow Dr. Creighton 

 in his speculations regarding the nature of these functions. 

 For in addition to its formative and respiratory functions, 

 the multifarious duties of lymph are now ascribed to this 

 single and comparatively simple material. The arguments 

 that lead to this startling conclusion are extremely curious 

 to follow. He finds that in snails and slugs which have 

 been specially worked at, glycogen is chiefly deposited 

 in certain connective tissue corpuscles, which are desig- 

 nated plasma cells. These are principally arranged along 

 the course of the blood-vessels, and in some instances 

 they form a complete coating to the vessels. This is 

 considered to indicate the existence of a primitive 

 lymphatic system. If this is so, there should be evidence 

 in the higher molluscs that this becomes more perfect, 

 and the different stages in the evolution of the lymphatic 

 vessels should be capable of demonstration. There is, 

 however, no attempt to do this ; in fact, it is admitted 

 that in the highest molluscs, the cephalopods, which have 

 a very perfect vascular system with arteries, veins and 

 capillaries, this arrangement of the plasma cells does 

 not occur, and these animals have little or no glycogen 

 in their tissues. Moreover, if the arrangement and 

 chemical construction of the plasma cells of the snail 

 has the great morphological value attached to it by Dr. 

 Creighton, it is remarkable that it is not found through- 

 out the class of gastropod molluscs, to which the snail 

 belongs ; it is apparently limited to quite a few members 

 of the group. So much importance is attached to this 

 idea by the author, that he almost seems, though his 

 words are not quite clear on this point, to assume that 

 the snail and slug are, in the line of descent, very near 

 ancestors of the vertebrate family. There is no attempt 

 to show the links in the chain, nor to explain why an 

 exceptional and almost accidental arrangement of con- 

 nective tissue cells in one or two isolated molluscs should 

 confer this honour upon such isolated specimens. We 

 do not think that a theory of this kind will do much to 

 shake the thoroughly well-grounded work of Haeckel and 

 other morphologists. 



To the physiologist the next conclusion drawn will be 

 even more startling ; it runs as follows : if the plasma 

 cells represent a lymph system, the glycogen of those 

 cells must represent lymph. It hardly seems worth while 

 to argue against such an unwarrantable suggestion. Any 

 other constituent of the plasma cells might equally well 

 have been selected. Lymph is a complex fluid acting as 

 a middle-man between blood and tissue elements ; it is 

 contained in spaces between and around the cells, not in 

 the interior of their cell-substance. If one seeks for an 

 analogy between the two mobile fluids of the vertebrate, 

 in the invertebrates it will be found much more easily in 

 many members of the worm group which have coloured 

 blood in their vessels, and colourless fluid in certain parts 

 of their body-cavity. 



Dr. Creighton's production, therefore, though interest- 

 ing as a record of observations, is most disappointing so 

 far as conclusions are concerned. Wide, sweeping, almost 

 revolutionary theories are advanced without a shred of 

 NO. 1590, VOL. 61] 



real evidence to support them. If the book serves no 

 other purpose, it will at least act as a warning example 

 of the danger of drawing hasty generalisations from im- 

 perfect data, data gathered from the exclusive study of 

 one particular small point with one exclusive method. 



OUR BOOK SHELF. 

 The Elements of Alternnting Currents. By W. S. 



Franklin and R. B. Williamson. Pp. 212. ^New 



York : The Macmillan Company. London : Macmillan 



and Co., Ltd., 1899.) 

 In this book will be found a very fair resume of the 

 theory and practice of alternate current working, and of 

 the modern developments associated with the use of 

 polyphase currents and the induction motor. 



It is interesting to compare a work such as the present, 

 characteristic as it is of American methods, with similar 

 works published in this country. Messrs. Franklin and 

 Williamson's treatment of their subject is distinguished 

 by conciseness, and by the almost total exclusion of any- 

 thing of historical interest, though the authors, in the 

 preface, acknowledge their great indebtedness to Stein- 

 metz, " whose papers are unique in their close touch with 

 engineering actualities." The beginner will, perhaps, 

 find that the brevity of treatment renders the theory, and 

 the usually excellent graphical constructions, here and 

 there obscure. But, on the other hand, the comments 

 upon the practical aspect of each question taken up are 

 of great value, especially to readers in this country, where 

 experience with polyphase currents is limited to some 

 half dozen installations of but few months standing. 



Continental engineers, accustomed to use the well- 

 known Hartmann and Braun instruments, will be aston- 

 ished to learn that " the only hot-wire instrument which 

 is much used is the Cardew voltmeter." Under the 

 heading " Revolving Contact Makers," the only form 

 described is that using a jet of conducting liquid making 

 contact with a revolving pin connected through the shaft 

 of the alternator ; while the much more convenient form 

 with two brushes and a revolving piece of metal let into 

 an insulating disc, which enables an electrostatic volt- 

 meter to be momentarily connected across a«y two points 

 in the alternator circuit, is not mentioned. 



The chapters relating to the theory of the synchronous 

 motor, the rotary converter and the induction motor 

 contain information not easy to find elsewhere in acces- 

 sible form. The short concluding chapter on the trans- 

 mission of power, however, lacks a simple statement of 

 the relative amounts of copper required by different sys- 

 tems of electrical transmission, and the respective merits 

 of these systems as regards regulation. 



Much information is to be found in this book in small 

 compass, and it will prove of value to engineers engaged 

 in alternate current practice. D. K. M. 



Oysters and Disease: An Account of Certain Observ- 

 ations upon the Normal and Pathological Histology 

 and Bacteriology of the Oyster and other Shellfish. By 

 Profs. W. A. Herdman, D.Sc, F.R.S., and R. Boyce, 

 M.B. Lancashire Sea Fisheries Memoirs. No. i. 

 Pp. 60 ; 8 plates. (London : George Philip and 

 Son, 1899.) 

 The monograph before us gives the results of three years' 

 work by the authors on oysters and disease. This thesis 

 is, of course, by no means new to either the general 

 scientific reader, the medical officer of health, or, indeed, 

 the general public. Oysters have for several years been 

 suspected, and, indeed, in some cases almost proved, to 

 be the source of typhoid fever. A most interesting report 

 was issued upon this subject by the Local Government 

 Board, which, if the reviewer remembers rightly, was 



