Progress of Rational Pathology. 237 



ness as the consequence of a kind of poisoning by them. 

 Henle, on the contrary, from his discoveries in fermentation 

 and putrefaction, and regarding the muscardine of silk worms, 

 is led to the conclusion, that infusoria and the lower forms 

 of plants are the sources of contagion, and cause disease by 

 the presence of their germs in the body : it is therefore neces- 

 sary to determine the existence of contagion and miasma, 

 their forms and organisation, and the course of miasmatic and 

 contagious diseases. Henle divides the diseases to which a 

 miasmatic or contagious origin is ascribed, into the three 

 following groups: — 1. Pure miasmatic disease (intermittent 

 fever) : in it miasma has not been detected either in or out of 

 the body: it does not wander, but remains fixed in certain 

 localities : there are no proofs, that it is inorganic, ra- 

 ther than a physical agent. 2 Miasmatico-contagious di- 

 seases (such as small-pox, measles, scarlet fever, typhus, &c.) 

 arise from miasma (i. e. from something injurious in the 

 air,) and also from contagion (i. e. something injurious de- 

 rived from a sick body.) The miasma and the contagion 

 of the same disease must be identical in their nature, (for like 

 effects have like causes) : the contagions of all these diseases 

 are transient, and therefore it is probable that what is called the 

 miasma (or infecting material of these diseases) is only a tran- 

 sient contagion, or vice versa. 3. The purely contagious diseases 

 (syphilis, itch, &c.) which never occur from miasma, have a 

 contagion which is not transient. The cause of miasmatico- 

 contagious diseases, appears as contagion or miasma, accord- 

 ing as its origin can or can not be traced from a sick body. 

 The fixed contagion of purely contagious diseases is infectious 

 matter, contained in a solid or a fluid substance taken from the 

 diseased body, commonly mucus or slime. It is thus, pro- 

 perly speaking, not contagion itself, but only the vehicle 

 of it. The process by which it is prepared is the ordi- 

 nary one of inflammation. The vesicles, pustules, &c. which 

 contain the pus are the ordinary results of inflammation 



