THE BEGINNINGS OF LIFE. 357 



owing to the corpuscles acting after the manner of 

 mere dead ferments. They might incite certain changes 

 in the fluids with which they came into contact; and 

 these changes would culminate in the re-evolution of 

 new and independent organisms in the blood and 

 tissues generally, or in some parts of them — just as the 

 poisonous organic particle from the skin of a small-pox 

 patient incites spreading changes in the body of a 

 person with whom it com.es into contact — changes which 

 terminate in the re-evolution of a similar poison 1. 



The opposite notion — viz. that the communicated 

 disease is caused by the direct multiplication of the 

 organisms which act as contagious agents — is beset with 

 difficulties. Seeing how exceedingly common Psoro- 

 sperms are in the bodies of all kinds of animals even 

 in their natural or healthy condition, why should they 

 not multiply to an undue extent, and produce disease 

 in them ? Such organisms are probably swallowed by 

 most of us during each meal in which meat is taken, 

 and yet no harm ensues — they are probably just as 

 nutritious as the meat in which they are contained. 

 Speaking of their almost universal prevalence, Dr. Cob- 

 bold says : — ^Altogether, at two meals, I could not have 

 swallowed less than eighteen thousand of these Psoro- 

 spermise;' and he adds that those who consume ^beef, 

 mutton, and pork, eat these bodies every day, but take 



^ I have elsewhere {Appendix E, p. cxv) expressed the belief that 

 the germs of existing morbid growths also operate in this manner when 

 they are the causes of ' secondary growths.' 



