PHYSIOLOGY. 99 



cupied pathologists much more than those of the former class ; 

 but the subject has been treated imperfectly in two respects. 



" First : It has been common to consider every convulsive or 

 spasmodic affection in an unusual degree, as an instance of in- 

 creased mobility. But often, the mobility being given, the 

 spasm or convulsion produced is merely the effect of the stimu- 

 lus applied, which may be capable of producing it in any person, 

 though more readily where there is a certain degree of mobility; 

 and, in several instances, we find that these effects are more con- 

 siderable in proportion to the increased tone and vigour of the 

 system, as in the case of tetanus ; so that it is false to consider 

 these preternatural motions as always a mark or effect of mo- 

 bility alone. Secondly: I think the case of mobility has been 

 improperly considered, as being the same with sensibility ; this, 

 I humbly allege, is the fault of Dr. Gaubius. I acknowledge 

 that increased sensibility and increased mobility are very com- 

 monly conjoined, and increased sensibility is to be mentioned as 

 the first cause of irritability ; but it is necessary to be observed, 

 that increased sensibility is not the sole cause of it, increased | 

 sensibility and mobility may be considered as different affections ; 

 an illustration of which I take from the power of custom with 

 regard to impressions made upon the stomach, or other parts of 

 the system, where the impression may be considered not only as 

 giving sensation, but as producing motion. 



" A second cause of irritability is a state of debility in the 

 moving fibres. Children and women are more moveable than 

 adult men ; and debility is a cause of increased mobility. I have 

 pointed out increased sensibility as conjoined in these cases, but 

 certainly debility is also present, and therefore may have its 

 share. There are many instances of persons weakened by oc- 

 casional causes, as fatigue, evacuations, preceding diseases, &c., 

 where the debility is very evident, while the change in the sen- 

 sibility is by no means so observable ; and therefore I say that 

 in the connexion of the ' delicata solidi compagis teneritas' 

 with both sensibility and irrritability, the latter is more con- 

 nected with debility than with sensibility. 



" A third cause of irritability is a subtile and theoret- 

 ical one ; but you will excuse me in taking up a moment of your \ 

 time in throwing it out ; viz. such things as give excitement 



