242 p. MAN80N ON THE PERIODICITY OF 



cloud, or rain, or other condition influencing the quantity or kinds 

 of rays infringing directly on the human body, at least so far as I 

 can see ; but with terrestrial magnetism the case is quite otherwise. 

 Its variations are rhythmical. If you consult authorities on the 

 diurnal variations of the declination and inclination of the compass, 

 and intensity of terrestrial magnetism you will find a marvellous 

 correspondence between the rhythm of these phenomena and that of 

 filarial periodicity. For example, the needle of the compass crosses 

 the magnetic meridian, or mean daily position, between the hours 

 of nine and ten a.m. and six and seven p.m. ; during the night and 

 early morning the north end of the needle is to the east of the 

 meridian, during the day to the west, and the hours when the meri- 

 dian is crossed correspond pretty closely to the times of change from 

 rest to activity, and vice versa of the filaria embryos. 



Again the minimum of daily change of terrestrial magnetic in- 

 tensity is between the hours of ten and eleven a.m., and the maxi- 

 mum between four and seven p.m., varying slightly with the season 

 of the year. These hours correspond very closely with those of 

 commencing rest and activity of the filaria in the normal state of the 

 body. There is no proof wliatever that there is any cause and eifect 

 relation between these two phenomena, but the coincidence is most 

 striking, and suggests further investigation. If experiment should 

 show such relation it would be interesting to know if the cause 

 operated directly, or if the effect on the embryos depended on 

 physiological changes on the body the result of terrestrial 

 magnetism. 



These may seem wild and unjustifiable speculations, but I only 

 offer them for what they are worth, and desire to separate them by 

 a clear and well-defined line from my facts. But the imagination 

 lias its place in science, I believe, as well as rigid observation and 

 induction. At any rate, actuated by these speculations, I have 

 made one or two crude and unsuccessful experiments. I wish very 

 much some expert in physiology and electricity would take the 

 matter up. My knowledge is so limited, and the apparatus I can 

 command so rude, that I despair of being able to give the answer 

 myself. I believe a systematic examination of the compound force 

 called light, or of terrestrial magnetism in their influence on these 

 worms, would give most valuable results, not only in solving this 

 most interesting problem, but in opening new and fertile fields in 

 physiology and pathology. 



