FILARIAL MIGRATIONS TO AND FROM THE CIRCULATION. 24 I 



body generally corresponds to these hours ? If you refer to my 

 chart you will find no explanation in the rapidity of the circulation, 

 nor in the temperature of the body. For sometimes the pulse is 

 quick when the embryos are numerous, and sometimes it is slow ; 

 sometimes the temperature fluctuates a degree without apparent 

 effect on the numbers circulating. 



Whatever the cause may be it certainly operates throvgh the 

 body, the medium in which the parasites are, but I very much in- 

 cline to think that though operating through the body it is placed 

 outside of it 



Of one thing we may be quite certain — that from the fact of the 

 periodicity being one of 24 hours its remote cause is the rising and 

 setting of the sun, or rather the altered relation of the earth's sur- 

 face to the sun recurring every 24 hours. Of another thing we may 

 also be certain, that the immediate cause is applied between the 

 hours of five and seven p.m. What, then, is the phenomenon in 

 nature which, depending on the position of the earth's surface to 

 the sun, begins to operate on the human body with the utmost 

 regularity between the hours of five and seven p.m., increases in 

 power up to midnight, wanes towards morning, and finally ceases to 

 act between nine and ten a.m. ? A correct answer to this would be 

 a step towards the solution of this strange problem ; only a step 

 however, for the method of its operating would still remain to be 

 explained. 



We may dismiss at once the diurnal variations of atmospheric 

 temperature and pressure, for, although, especially in these latitudes, 

 these daily ranges are pretty constant, yet when completely in- 

 verted as sometimes happens, and as you may see from a comparison 

 of the chart and meteorological register, there is no corresponding 

 disturbance in filarial periodicity. 



In casting about for the answer two things occur to me. 1st. 

 The rays emanating from the sun undergo about these hours marked 

 alteration in their proportions and power. 2nd. The magnetic con- 

 dition of the earth suffers a change about the same time. 



I am inclined to dismiss the former as the direct cause, for were 

 the sun's rays the direct regulating inJlMence we might expect to find 

 the rhythm answered by the embryos affected by the presence and 

 absence of clouds and so forth. This is far from being the case, as 

 you can see by comparing the chart with the meteorological register. 

 The periodicity bears no relation whatever to the hours of sunshine, 



