Mav 



1895] 



NA TURE 



8? 



and typhoid bacilli respectively. \'arious imints were investigated 

 as tn whether insolation previous to inoculation increased the 

 animal's susceptibility to these diseases, also what was the efifect 

 of insolation on the animal after infection, and whether the same 

 results were obtained when the temperature of the surrounding air 

 during insi>lation was not permitted to rise. The toxic properties 

 of the cholera and typhoid broth cultures employed w'ere care- 

 fully tested, and it was ascertained that the lethal dose in the 

 case of cholera, procuring death in twenty-four hours, was secured 

 by employing cultures in the jirfjportion of 0'20 per cent of the 

 weight of the animal operated upon, whilst to obtain similar 

 results with typhoid cultures, 0"40 per cent, of the weight of the 

 animal was the proiiorlion in which they had to be used. 



In the case of Ijoth cholera and typhoid it was found that 

 previous exposure to sunshine increasetl the animals' susceptibility 

 to these diseases, for not only did they die more rapidly when 

 subsequently inoculated with these cultures than the guinea-pigs 

 similarly treated, exposed, however, only to diffused light, but they 

 succimibed t^i smaller doses, and doses which did not prove fatal 

 to the guinea-pigs which had been previously protected from 

 simshine. When the exposure to sunshine took place after 

 infection fatal results were greatly accelerated, for instead of 

 dying in from 15 to 24 hours they succumbed in from 3 to 5 

 hours. These experiments were, however, open to the objection 

 that the accelerated lethal action through subsequent insolation 

 might be due to the higher temperature which necessarily 

 prevailed in boxes exposed to sunshine over those to w'hich 

 diffused light only was admitted. To dispose of this difficulty, 

 boxes were constructed with double cases through which a 

 current of water was kept circulating ; in the " sunshine " boxes, as 

 before, only glass was used, whilst in the "diffused light" boxes 

 the outer case was made of zinc. In spite, however, of these 

 precautions as regards temperature the results confirmed those 

 previously oljtained, the insolated animals still exhibiting the 

 .same increased susceptibility to infection from these diseases over 

 the non-isolated animals. 



Dr. Masella does not attempt to give any explanation of the re- 

 markable results he has obtained, but we would suggest that the 

 action of simshine should be tried on anti-toxines. It would be 

 of great interest to ascertain how the jjotency of these protective 

 fluids outside the body was affected by exposure to sunshine, and 

 also what residt, if any, isolation had on their generation within 

 the animal .system. 



VVc know that the toxic jiroperties of, for example, tetanus 

 •cultures may be entirely destroyed in from 15 to 18 hours in 

 direct sunshine at a temperature of from 35° to 43° C, and Koux 

 an<l Versin state that five hours' direct insolation greatly modifies 

 the toxic properties of diphtheria cultures ; again, Calmette has 

 foimd that afler two weeks' insolation the poison of the N^aya 

 tripiuiiaiis is completely destroyed, whilst a similar exposure has 

 a damaging effect on the poison of the rattlesnake. .So far as 

 we are aware, the action of sunshine on the immunising properties 

 of serum has not been investigated, and its study should prove of 

 immense interest and importance. 



The results obtained by De Renzi with tuberculous infection 

 have a [iraciical confirmation in the acknowledged benefit which 

 patients .suffering from tuberculosis derive from residence in ])laces 

 such as Davos, where the niaxinumi amount of sunshine may be 

 secured. On the other hand. Dr. .Ma.sella's experiments leave 

 us with an uucomforlable uncertainty as to the wisdom of basking 

 in the sunshine. He would have us believe that his investigations 

 explain the greater prevalence and virulence of typhoid and cholera 

 (which he si.-iies as an accepted fact) in hot countries where the 

 sun .shines with greater power and more continuously, .\fterall, 

 our smoke laden atmosphere and dreary yellow fogs may be 

 turned to account seemingly, and the London water companies 

 may congratulate themselves that the.se two water-borne dise.i.ses, 

 par i\\celkiic,\ may be made to yield not only to efficient ]nirifying 

 processes at their hands, but that such an unexpected ally, 

 according to Dr. Masella, is to be found in the limited amount 

 of sunshine which Londoners can enjoy ! 



G. C. Frankland. 



THE CONSTRUCrrON OF STAND I /H> 



THERMi )ME TERS. 

 SLRIK.S of important articles on the preparation and testiAg 

 of standard thermometers have been communicated to the 

 Zetlsihrift pir Jnstrunuiitcikiimie by Drs. Pernet, Jaeger, and 

 Oiimhch, of the I'hysikalisch-Technische Reichsanstalt. The 



A^ 



selection of the best glass, the calibration ol the thennometers, 

 the determination of the coefficients of external and internal 

 pressure, and the verification of the principal points are fully 

 dealt with. One source of error in thermometers as usually con- 

 structed, lies in the fact of the bulbs being blown from the tubes. 

 The vaporisation of certain constituents of the glass during this 

 operation leads to a difference of chemical constitution between 

 the stem and the bidb. This may be obviated by making the 

 bulbs out of thin walled tubes of the .same kind of glass, ami 

 welding them on to the stems. As regards the depression of the 

 freezing point, it was found by Wiebe and Schott, of Jena, that 

 glasses containing either sodium or pota: ium, but not both, 

 showed this after-effect to the least extent. ii order to render 

 the reading of temperatures accurate to within o'-oo2, the length 

 of a degree should not be less than 6 mm., and since the length 

 of the stem cannot conveniently exceed 60 cm., the range of 

 measurable temperature is practically limited to 100°. Stem 

 thermometers without enamel backs or enclosing tubes were the 

 only ones found suitable for first-class standards. When certain 

 fixed ]X)ints outside the scale were to be brought in, this wa-s 

 accomplished by widening out the tube above them. An equal 

 linear division of the scale was adopted, this having great 

 advantages over the more or less untrustworthy division by equal 

 volumes. For calibration, threads of mercury of different leng+hs 

 were cut off from the main portion and measured with micrometer 

 microscopes, viewing them both through the face and the back of 

 the stem. But the threads were not cut off by local heating, 

 since that is apt to produce a permanent change of capacity. The 

 small and almost microscopic bubble which remains in every 

 thermometer was made use of. It was brought to the entrance 

 of the bulb when the desired portion of the thread had been 

 driven into the stem, and then a slight jerk sufficed to cut off 

 the required length. To facilitate this operation, the bulb was 

 narrowed to a neck at the entrance to the stem. As regard.s 

 pressure, two factors had to be considered. The external 

 atmospheric pressure, and the pressure of the liquid in which it 

 is immersed, tend to compress the glass vessel and to produce an 

 apparent elevation of temperature. The capillary pressure of the 

 mercury, and its hydnistatic pressure, on the other hand, tend to 

 widen the bulb and produce an apparent cooling. The first of 

 these elements was investigated by exposing the thermometer to 

 various high and low pressures in a glycerine bath, and the 

 second by observing the readings when the thermometer stood 

 horizontally and vertically respectively, at its highest measurable 

 temperature. The ca|iillary jiressure was found to be too capri- 

 cious to be accurately measured, but it is a negligible quantity. 

 The coefficient of apparent expansion of mercury in the new- 

 Jena glass thermometer 16'" was found to be o-oooi57i 

 between 0° and 100°. 



NO. 



1334, VOL. 52] 



THE INFLUENCE OF MAGNETIC FIELDS 

 UPON ELECTRICAL RESISTANCE. 



TT is well known that the resistance (R) of a wire of bismuth, as 

 measured with a constant current, increa-ses under the influence 

 of a magnetic field, and that this increase depends on the strength 

 of the field and its direction with reference to the current in the 

 wire. If the current traversing the ijismuth is oscillatory, the re- 

 si.slance has a value O outside the magnetic field, or in a field in 

 which the lines of force are parallel to the wire which is less than 

 R. If, however, the wire is perpendicular to the lines of force 

 of a field greater than 6000 C.C'...S. units, the resistance O is 

 greater than R ; the difference O - R increases from this point 

 pretty rapidly as the strength of the field increa.ses. "Thesie 

 changes are not due to alterations in the self-inductor, since they 

 are independent of the form of the bismuth spiral. This curious 

 phenomenon has lately been examined by M. I. Sadovsky 

 ( Totinial dc la Socii'ti' PhysiiO-Chemii/in- di Ru$se. xxvi. 1894, and 

 fournal dc Pltysitjiic, April 1895), who sums up the results of his 

 experiments as follows: (i) The difference in the resistance of 

 bismuth observed with constant or alternating currents is measm-- 

 able outside a magnetic field with 300 alternations per second, 

 and can be detected in nuignetic fielils with only three or four 

 alternations per second ; (2) this difference depends on the 

 number of o.scillations per second, and without the magnetic 

 field increases with the increase in the frequency of the alterna- 

 tions ; (3) the resi.slance which bismuth, in a strong -magnetic 

 field, offers to an increasing current is greater, and that to a de- 

 creasing current less than the resistance fin- steady currents. The 

 difference between the resistances loan increasing and decreasimj 



