SECT. XXXIII. 2. 9. OF SENSATION. 313 



creating the abforption of the matter in the ulcufcles of thofe 

 difeafes, and thence difpofing them to heal ; which would other- 

 wife continue to fpread. 



Why the venereal difeafe, and itch, and tinea, or fcald head, 

 are repeatedly contagious, while thofe contagions attended with 

 fever can be received but once, feems to depend on their being 

 rather local difeafes than univerfal ones, and are hence not at- 

 tended with fever, except the purulent fever in their laft ftages, 

 when the patient is deftroyed by them. On this account the 

 whole of the fyftem does not become habituated to thefe morbid 

 actions, fo as to ceafe to be affefted with fenfation by a repetition 

 of the contagion. Thus the contagious matter of the venereal 

 difeafe, and of the tinea, affefts the lymphatic glands, as the in- 

 guinal glands, and thofe about the roots of the hair and neck, 

 where it is arrefted, but does not feem to affedl the blood-veflels, 

 fince no fever enfues. 



Hence it would appear that thefe kinds of contagion are prop- 

 agated not by means of the circulation, but by fympathy of dif- 

 tant parts with each other ; fince if a diftant part, as the palate, 

 (hould be excited by fenfitive affociation into the fame kind of 

 motions, as the parts originally affedled by the contadt of infec- 

 tious matter ; that diftant part will produce the fame kind of 

 infectious matter ; for every fecretion from the blood is formed 

 from it by the peculiar motions of the fine extremities of the 

 gland, which fecretes it ; the various fecreted fluids, as the bile, 

 feliva, gaftric juice, not previoufly exifling, as fuch, in the blood- 

 veflels. 



And this peculiar fympathy between the genitals and the 

 throat, owing to fenfitive aflbciation, appears not only in the 

 production of venereal ulcers in the throat, but in a variety of 

 other inftances, as in the mumps, in the hydrophobia, fome 

 coughs, ftrangulation, the production of the beard, change of 

 voice at puberty, which are further defcribed in Clafs IV. i. 2. 7. 



To evince that the produdion of fuch large quantities of con- 

 tagious matter, as are feen in fome variolous patients, fo as to 

 cover the whole (kin almoft with puftules, does not arife from 

 any chemical fermentation in the blood, but that it is owing to 

 morbid motions of the fine extremities of the capillaries, or 

 glands, whether thefe be ruptured or not, appears from the quan- 

 tity of this matter always correfponding with the quantity of the 

 fever ; that is, with the violent exertions of thofe glands and 

 capillaries, which are the terminations of the arterial fyftem. 



The truth of this theory is evinced further by a circumftance 

 obferved by Mr. J. Hunter, in his Treatife on Venereal Difeafe ; 

 that in a patient, who was inoculated for the fmall-pox, and 



VOL. I. R R who 



