PHYSIOLOGY. 101 



periodical. The power of habit, in giving such laws in pro- 

 ducing periodical revolutions, is especially remarkable in dis- 

 eases which are most certainly periodical, i.e. intermittent fevers; 

 a proof of which we have in the direction which Celsus gives 

 * diu meminisse oportet diem et horam ;' it appears, by 

 the most exact observations, that intermittents continue their dis- 

 position to recur at the usual period ; that though they should 

 cease for a fortnight together, when they recur, it is not only 

 on the day, but at the hour they usually did ; therefore, says 

 Celsus, a patient ought to be long attentive not to admit, 

 at these times, any occasional cause that might excite the dis- 

 ease. And I must add another observation that is of use and 

 curiosity also, that such is the apparent spontaneity that takes 

 place with regard to repeated motions, that the slightest associ- 

 ations serve, upon occasion, to renew them ; and even the me- 

 mory of them is sufficient to bring them back. When I men- 

 tioned the power of memory, and its being limited with regard 

 to sensations, I said that we recall only those of sight and hear- 

 ing with any exactness, and but a few of those of touch; but even 

 those of smell and taste can be in some measure renewed; thus, a 

 person who has taken ipecacuan and is vomited with it, cannot 

 recall the particular taste of it ; but he can renew the sense of the 

 disagreeable, the memory of the' nausea, and that will in many 

 persons arise to vomiting ; and this explains what appears very 

 marvellous, that persons can recall at pleasure both epileptic and 

 hysteric fits. There has been a question with regard to this epilep- 

 sia simulata, whether it is real ? I believe the fits are as real as the 

 original ones, and are only simulated with regard to their cause, 

 as we know to be the case where they can be cured by exor- 

 cisms. I have a sort of observation to make with regard to real 

 associations bringing on a variety of convulsive affections, as 

 HI the case off ear 9 especially where it is produced by surprise; we 

 should expect that the law of sensibility should take place here, 

 and that the association should have less and less effect; but in 

 some instances it continues for life, and seems to gain strength. 

 2. Another case in which habit has the effect of giving more mobi- 

 lity, is a strictly uniform manner of life, the ' strictius regimen' of 

 Dr. Gaubius; for, as new impressions are, cceteris paribus, always 

 the strongest, persons of the least experience will be most exposed 



