FUNCTIONAL INERTIA AS LATENT PERIODS, &c. 51 



writing of hemicrania, says : " The attacks may occur 

 on the same day every week, every fortnight or 

 every month/' and Dr. Mackenzie* says of it, " One 

 of the most peculiar features of these cases is the 

 periodicity of the attacks. Many patients know 

 when an attack is due, although there may be no 

 premonitory symptoms." There is then here a 

 weekly, bi-monthly or monthly rhythm a rhythm 

 independent of the environment something due 

 to the functional inertia of the organism as a whole. 

 In 1902 I published an analysis of certain records of 

 hemicranial headache kept for three years by the 

 patient himself, and from these I fully demonstrated 

 the rhythmic character of the morbid metabolism 

 here involved. After noting the precise periodicity 

 mostly bi-monthly- I remarked, " These results are 

 sufficiently striking when we remember what a 

 degree of constancy of phasic metabolic condition 

 this indicates amidst the greatly altering environ-* 

 mental conditions extending over three years." We 

 have but to glance at the changing occupations of 

 the professional man in question his ordinary work 

 during the day, with dining at home, or dining out 

 in the evening, attending public dinners or entertain- 

 ments, breathing good air and bad, making speeches 

 or listening to them, travelling by land or sea, having 

 meals at irregular hours and meals varying in quality 

 and quantity, having hours of sleep curtailed, &c. 

 in order to see that the environment frequently 

 altered without any corresponding alteration in the 



* In Clifford Allbutt's " System of Medicine." 



