Progress of Rational Pathology. 241 



(if the parasite has no disposition to spread beyond the 

 points of inoculation, or if it is tied down to certain parts 

 of the body,) and general. In the latter, the following 

 conditions may occur : — a. the parasite spreads over the 

 whole surface of the body or over the greater part of it : 

 b. it may not be the parasite itself, but the diseased con- 

 dition of the skin induced by it, that spreads by continuity and 

 by sympathy : c. the parasite passes into the blood, and through 

 it into all organs : d. the parasite, in the place in which it is 

 fixed, may act on the blood circulating through that spot, and 

 so at last get into the general circulation : e. the symptoms of 

 a disease of the whole system manifest themselves by means of 

 the sympathy of the nerves. 6. In relation to the seat or germ- 

 beds of contagion, parasites may be divided into three classes — 

 a. parasites of the inner and outer surface of the mucous linings 

 and of the skin : to this belong itches, tinea, and most miasma- 

 tico-contagious diseases ; their passage into the blood is possi- 

 ble, but not necessary : b. parasites of the fluids ; here the 

 blood and the secretions are the vehicles of contagion ; the 

 eruption is wanting or is unimportant : to this belong hydro- 

 phobia and possibly the plague : c. parasites which grow on the 

 skin as well as in the fluids, which begin by germinating on the 

 skin, but usually pass into the fluids, as glanders and syphilis. 

 7. The course of contagious and miasmatico-contagious 

 diseases is as follows : The parasite is taken up by the mucous 

 membrane or injured skin ; if the quantity taken up be small, 

 then follows the stage of latent contagion, during which 

 the parasite grows and multiplies. Neither does a skin para- 

 site disappear in the blood, to be deposited afterwards on the 

 skin, nor does a blood parasite remain inactive till the disease 

 breaks out, (as people believe of hydrophobia). When the 

 operation of the parasite is powerful (in the beginning of epi- 

 demics) death often occurs rapidly, and perhaps by sudden 

 alteration of the blood, or by suffocation from irritation of the 

 minutest bronchi.— The skin parasites cause mortification 



