September 3, 1891] 



NATURE 



419 



mined by a sub-committee appointed for the purpose of 

 preparing a specification for the construction and use of 

 the cell, is stated to be r433 volts at the temperature 

 62" F. By means of this cell and known resistances, it 

 will be possible to calibrate instruments without the use 

 of electrolysis, and this to many persons would be the 

 readiest and most easily carried out method. Of course, 

 logically speaking, the standard of electromotive force is 

 settled when those of resistance and current are fixed, 

 and thus, if the order of definition is adhered to, the cell 

 does not come in. But its electromotive force having 

 been determined by careful measurement, and found to 

 be so constant as it is, and so consistently the same in 

 different specimens when the mode of construction is 

 carefully attended to, it is too valuable a standard of 

 reference to be set aside. 



A very interesting discussion took place as to the mode 

 of preparing these cells, and on the experience of different 

 investigators as to their behaviour. Some of the di- 

 vergences stated in the discussion were probably due to 

 the different degrees of manipulative skill possessed by 

 the various observers. A few careful experiments with 

 different batches of cells carried out personally by the 

 members of the committee interested in the matter 

 would set the question at rest, and probably entirely 

 confirm Lord Rayleigh's marvellously consistent results. 



A side-point which came out in discussion is worthy of 

 notice. We have not in this country any legal definition 

 of temperature, whether Centigrade or Fahrenheit. In 

 the definition of the standard yard 62'' Fahrenheit is 

 specified, but there is nothing to tell how that tempera- 

 ture is to be determined. It is well known (though ap- 

 parently not to some of the text-book writers on heat) 

 that mercurial thermometers, made with different kinds 

 of glass, while agreeing at the freezing and boiling points, 

 agree nowhere else, and all differ more or less from the 

 air-thermometer. In very accurate work these discre- 

 pancies become very important, and thermometers must 

 be calibrated by means of standards, if their indications 

 are to be of any use for comparison. Some legal defini- 

 tion of temperature will, ere long, have to be given, and 

 it seems rather a pity that the Committee did not prac- 

 tically settle this by saying what they meant by 62° 

 Fahrenheit. 



The definition of the volt for alternating currents, 

 embodied in Resolution 15, is, of course, a mere con- 

 sequence of Resolution 11, and these two definitions 

 taken together are specially applicable to the measure- 

 ment of the power spent in lighting incandescent lamps. 



We have only to note that the Committee, in Resolu- 

 tions 12 and 16, adopted instruments on the principle of 

 the balance for the measurement of currents, and on the 

 principle of Sir William Thomson's quadrant electro- 

 meter, used idiostatically, for the measurement of differ- 

 ences of potential, except for large differences, when an 

 electrometer on the principle of the balance is to be em- 

 ployed. Thus the beautiful electrometers invented long 

 ago by Sir William Thomson are likely to become at 

 last, in a modified form. Board of Trade standards of 

 exact measurement in industrial electricity. This is by 

 no means the only striking example which could be cited 

 of the thoroughly practical, because thoroughly theo- 

 retical, character of the instruments invented by one 

 NO. I 1 40, VOL. 44] 



who understands all sides of the difficult problem 

 involved in the invention and construction of such 

 apparatus. 



No resolutions were framed by the Committee on the 

 very important subject of the measurement of power and 

 energy. This must, however, come to the front before 

 very long, and will tax the resources of the standardizing 

 laboratory and its officials, assisted, as no doubt they will 

 be, by Committees such as this which has just reported. 

 We congratulate the Committee on the results of its 

 labours, and trust that the requisite Order in Council will 

 be passed before long confirming its resolutions. The 

 laboratory will then be able to get to work, the necessary 

 standards which have been asked for so long will be made 

 accessible to those engaged in the electrical industries, 

 and some serious difficulties under which they have 

 laboured, in supplying electric light and power to the 

 public, will be at last removed. 



THE CONGRESS OF HYGIENE. 

 '\\TY. print to-day a report of the important discussion 

 **^ in Section II. (Bacteriology) of the Congress of 

 Hygiene, on " Immunity, Natural and Acquired": — 



Dr. Roux, of the Institut Pasteur, in an introductory address, 

 indicated the scope of the discu?sion. He began by saying that, 

 in inviting a pupil of M. Pasteur to open the discussion on this 

 subject, the Organizing Committee had reminded the Section 

 that the great amount of interesting work which had recently 

 been done on the subject had one point in common— namely, 

 the attenuation of virus, and preventive inoculation, the two 

 subjects with which M. Pasteur's name would for all iime be 

 honourably associated. With the single notable exception of 

 vaccination, the only way of conferring immunity against any 

 disease was the inoculation of the virus of the disease. To the 

 old dangerous method of producing immunity by inoculation, 

 Pasteur had added the less dangerous one of preventive inocula- 

 tion by means of an attenuated virus, to which he had applied 

 the term vaccination. The designation "attenuated" virus 

 ought to be reserved for virus weakened without being attenuated 

 — for example, by artificially lowering the vitality of the organisms 

 for producing it. 



Methods of Atlenuation. — Two methods of attenuation had been 

 described by M. Pasteur — namely, the prolonged exposure of a 

 culture to air at a suitable temperature, and the passage of the 

 micro-organisms through the bodies of different species of 

 animals. Other methods had also been employed — for example, 

 the action of heat, the use of antiseptics, of compressed oxygen 

 and light. 



In all cases, whatever the method employed, it was found to 

 be necessary that the attenuation should be effected slowly and 

 gradually ; rapid attenuation rendered a virus altogether inactive 

 without impressing on it any hereditary weakness. In whatever 

 way the virus was prepared, it must, in order to confer immunity, 

 be brought into direct contact with the tissues of the animal. In 

 the early experiments the virus employed was always living ; the 

 living microbe, itself attenuated as to its virulence, was used. 

 Another possible method of conferring immunity was the inocula- 

 tion of the chemical substances produced by the micro-organisms. 



Phagorytosis. — Dr. Roux next dealt with the doctrine of pha- 

 gocytosis associated with the name of Dr. Metchnikoff. This 

 observer had proved, by the study of the amoeboid movement of 

 certain cells that they possessed the power of including other 

 cells and bodies in their substance. The phagocyte cells origin- 

 ated in the mesoderm. They possessed, further, the property of 

 being able to digest the bodies which they had ingested. They 

 were, in fact, the only cells which manifested in the human body 

 any intracellular digestion. If the history of a bacterium in the 

 interior of a phagocyte were followed, it would be seen that it 

 underwent a peculiar series of alterations, very different from what 

 took place when a microbe died in cultivating fluids. Whether 

 a virulent virus was introduced into the bodies of animals which 

 resisted inoculation, or whether attenuated microbes were injected 



