204 REPETITION Sect. XXII. 3. 4. 



and produce an infectious faliva fimilar to that inflilled into the 

 wo and. 



Though in many contagious fevers a material fimilar to that 

 which produced the difeafe, is thus generated by imitation •, yet 

 there 'ire other infectious materials, which do not thus propagate 

 themfelves, but which feem to act like flow poifons. Of this 

 1 id was the contagious matter, which produced the jail-fever 

 at the aflises at Oxford about a century ago. Which, though 

 fatal to ib many, was not communicated to their nurfes or at- 

 tendants. In thefe cafes, the imitations of the fine veffels, as 

 a: i. -{bribed, appear to be imperfect, and do not therefore pro- 



duce a matter fimilar to that, which ftimalates them j in this 

 circumitaiice refembling the venereal matter in ulcers of the 

 throat or fkin, according to the curious difcovery of Mr. Hun- 

 ter above related, who iound, by repeated inoculations, that it 

 would not infcJL Hunter on Venereal Difeafe, Part vi. 

 ch. 1. 



Another example of morbid imitation is in the production of 

 a great quantity of contagious matter, as in the inoculated fmall- 

 pox, from a fmall quantity of it inferted into the arm. Thefe 

 particles of contagious matter ftimuiate the extremities of the 

 fine arteries of the fkin, and caufe them to imitate the motions 

 by which themfelves were produced, and thus to produce a 

 thoufand fold of a fimihr material. As different kinds of light 

 may be fuppofed to ftimuiate parts of the retina into different 

 kinds of motion, fo the application of different contagious 

 matters may be believed to ftimuiate the fine terminations of the 

 arteries into different kinds of motion, which may form matters 

 fimilar to themfelves. This is truly difficult to underfland, but 

 may be conceived to depend on this circumftance ; that- thofe 

 matters, which ftimuiate other bodies into action, and the bod- 

 ies thus fiimulated, muft poffefs fome common properties, as 

 fpoken of in Sect. XIV. 4. See Sea. XXXIII. 2. 6. Other 

 tances are mentioned in the Section on Generation, which 

 (hew the probability, that the extremities of the feminal glands 

 may imitate certain ideas of the mind, or actions of the organs 

 of fenfe, and thus occafion the male or female fex of the embryi 

 on. See Sect. XXXIX. 6. 



We come now to thofe imitations, which are not attended 

 with fenfation. Of thefe are all the irritative ideas already ex- 

 plained, as when the retina of the eye imitates by its action or 

 configuration the tree or the bench, which I fhun in walking pafl 

 without attending to them. Other examples of thefe irritative 

 imitations are daily obfervable in common life ; thus one yawn- 

 g perfoa fhali fet a whole company a yawning j and fome have 



acquired 



