04 REPETITION SECT. XXII. 3. 4. 



and produce an infeftious faliva fimilar to that inllilled into the 

 wound. 



Though in many contagious fevers a material fimilar to that 

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

 there are other infeftious materials, which do not thus propagate 

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

 kind was the contagious matter, which produced the jail-fever 

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

 fatal to fo many, was not communicated to their nurtes or at- 

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

 above defcribed, appear to be imperfea, and do not therefore 

 produce a matrer fimilar to that, which ftimulates them ; in 

 this circumftance refembling the venereal matter in ulcers of the 

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

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

 would not infed. Hunter on Venereal Difeafe, Part vi. 

 ch. i. 



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 ftimulate 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 fimilar material. As different kinds of light 

 may be fuppofed to ftimulate parts of the retina into different 

 kinds of motion, fo the application of different contagious mat- 

 ters may be believed to ftimulate the fine terminations of the 

 arterits into different kinds of motion, which may form matters 

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

 may be conceived to depend on this circumftance ; that thofe 

 matters, which ftimulate other bodies into aclion, and the bod- 

 ies thus ftimulated, muft poflefs fome common properties, as 

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

 inftances are mentioned in the Seaion on Generation, which 

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

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

 of fenfe, and thus occafion the male or female fex of the embry- 

 on. See Sea. XXXIX. 6. 



4 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 aaion or 

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

 without attending to them. Other examples of thefe irritative 

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

 Ifig perfon fhall fet a whole company a yawning j and fome have 



?cquire4 



