Au^. 19. 1875 



NATURE 



321 



the hind limb the mere act of extension is sufficient stimulus to call 

 forth a definite amount of response which takes the form of a 

 simple contraction, but that if the limb be held until this reflex 

 act has passed off there is no consciousness on the part of the 

 brain that the limb is in an unusual position, and consequently 

 no volition is exerted to remove it. 



It cannot be objected to this experiment that the stoppage of 

 the circulation in the hind limbs has diminished their irritability 

 because the frog A has perfect control over his ; and, moreover, 

 the vigour with which the reflex acts are executed in B precludes 

 this idea. Again, it might be said that the stoppage of the re- 

 spiration by the urari, and consequent supply of ill-aerated blood 

 to the brain has injured the volition of the animal ; to meet this, 

 two counter experiments have been tried : in one a frog was 

 gagged so as to keep its mouth open for some hours, and in 

 the other a frog was kept under well-aerated water for two 

 hours (a period equal to the duration of the chief experiment), 

 and in neither case did the frogs seem to suffer any inconve- 

 nience whatever, least of all did they lose their volition. 



In order to investigate the action of urari on the spinal cord, 

 two similar frogs were taken as before ; but previously to being 

 ligatured they were pithed and had their brains destroyed ; they 

 were then suspended, and the state of the cord, as manifested by 

 reflex action, tested ; dilute sulphuric acid was used as stimulus ; 

 the numbers represent quarter seconds. 



h. m. A* B 



From this it would appear that the first effect of urari is to 

 make the action of the cord uncertain, then to delay the reflex 

 action, and finally to destroy it entirely. The table has been 

 divided into three parts, o, |8, and 7, which seem to represent in 

 a tolerably typical manner the three stages into which the phe- 

 nomena are always divisible ; sometimes the animal recovered 

 after the stage 7. 



This short account of the above experiments is intended as a 

 preliminary notice. I am continuing investigations on mammals, 

 and puipose hereafter to publish a more complete account of my 

 results. " C. Yule 



Physiological Laboratory, Cambridge 



P. S.— Since writing the above my attention has been called to 

 a paper by Dr. J. Steiner, in Keicharfsund Du Bois-Kaymond''s 

 Archiv for July. He iftvestigates the action of urari on Inverte- 

 brates and tishes, and finds that among the latter its effect is to 

 destroy volition before the peripheral motor fibres are attacked. 



WEATHER AND EPIDEMICS OF SCARLET 

 FEVER IN LONDON DURING THE PAST 

 THIRTY-FIVE YEARS* 



n^HIS paper gives the results of an investigation, the purpose 

 -'■ of which was to determine whether the seasonal influence 

 of weather on deaths from scarlet fever, as shown by the curve 

 constructed from the figures of thirty years, would present itself 

 if the period were broken up and curves constructed for the 

 several smaller periods embraced in the long one. In other 

 words, the object was to determine whether, in the case of a 

 disease which is strongly epidemic, the obedience to seasonal 



* Abstract of a paper read by Dr. Arthur Mitchell at the general meeting 

 of the Scottish Meteorological Society, July 13. 



influences, would exhibit a steadiness and uniformity of cha- 

 racter, such as is presented in the case of pulmonary diseases. 

 In London there have been six epidemics of scarlet fever during 

 the last thirty-five years, reaching their maxima in 1844, 1848, 

 1854, 1859, 1863, and 1870. Curves were constructed repre- 

 senting the average weekly deaths from scarlet fever for each of 

 the six periods embracing these epidemics. These curves were 

 then compared with the curve for the thirty years, 1845-74, the 

 leading features of which are that it is above the average from 

 the beginning of September to the end of the year, and below 

 the average during the rest of the year ; and that the period of 

 highest death-rate is from the beginning of October to the end of 

 November, when it rises to about 60 per cent, above the average, 

 and the period of lowest death-rate in March, April, and May, 

 when it is about 33 per cent, below the average. 



On comparing the curves for the six short portions of the 

 thirty-five years, each dealing only with four, five, or six years, 

 with the general curve for the long period of thirty years, a re- 

 markable similarity is found to occur. They are all substantially 

 the same curve. The description of the general curve given 

 above applies almost literally to every one of the six curves for 

 short periods, and indeed so close is the correspondence that 

 they all cross their mean almost in the same week of the year. 

 In every case the maximum occurs in October and November, and 

 the only point of difference among them is that while the general 

 curve rises at the maximum period to 60 per cent, above the 

 average, during the first epidemic it rose only to 40 per cent , 

 and in one or two of the others it rose to 80 per cent, above the 

 average. The steady obedience to climatic influences in the 

 fatality from a disease so decidedly epidemic as scarlet fever is 

 very remarkable, and the more so inasmuch as no other disease, 

 with the single exception of typhoid fever, attains to its maximum 

 fatality in London under the conditions of weather peculiar to 

 October and November. 



PHYSICAL PROPERTIES OF MATTER IN 

 THE LIQUID AND GASEOUS STATES* 

 IL 

 Law of Gay-Lussac.—ThtLt the law of Gay-Lussac in the case 

 of the so-called permanent gases, or in general terms of gases 

 greatly above their critical points, holds good at least at ordinary 

 pressures, within the limits of experimental error, is highly pro- 

 bable from the experiments of Regnault ; but the results I have 

 obtained with carbonic acid will show that this law, hke that of 

 Boyle, is true only in certain limiting conditions of gaseous mat- 

 ter, and that it wholly fails in others. It will be shown that not 

 only does the coefficient of expansion change rapidly with the 

 pressure, but that, the pressure or volume remaining constant, the 

 coefficient changes with the temperature. The latter result was 

 first obtained from a set of preliminary experiments, in which the 

 expansion of carbonic acid under a pressure of seventeen atmo- 

 spheres was observed at 4°, 20", and 54° ; and it has since been 

 fully confirmed by a large number of experiments made at dif- 

 ferent pressures and well-defined temperatures. These experi- 

 ments were conducted by the two methods commonly known as 

 the method of constant pressure and the method of constant 

 volume. The two methods, except in the limiting conditions, 

 do not give the same values for the coefficient of expansion ; but 

 they agree in this respect, that at high pressures the value of that 

 coefficient changes with the temperature. While I have con- 

 fined this statement to the actual results of experiment, I have 

 no doubt that future observations will discover, in the case, at 

 least, of such gases as carbonic acid, a similar but smaller change 

 in the value of the co-efficient for heat at low pressures. The 

 numerous experiments I have made on this subject will shortly 

 be communicated in detail to the Society ; and for the present I 

 will only give the following results : — 



Expansion of Heat of Carbonic Acid Gas tuider high pressures. 



P-sure. ^^-Sui^-r^ L°i^:^aa'i.t°^ temperature.: 

 at. 



22*26 0*03934 i-oooo 6-051 



22-26 0-05183 i"3i75 63-79 [ ...(A) 



22-26 . ... 0-05909 1-5020 loo-io) 



* " Prehminary Notice of further Researches on the Physic.1l Properties 

 of Matter in the Liquid and Ciseous States under vatied conditions ol Pres- 

 sure and Temperature." Paper read before the Royal Society by Dr. 

 Andrews, F.R.S., Vice-President of Queen's College, Belfast. Continued 

 (rem p. 301. 



f 



