8 PHARMACEUTICAL BACTEEIOLOGY 



tion of this disease. That is, the " nitro-aerial " principle, which causes 

 or invigorates plant and animal life, is supposed to become vitiated. 



The corrupting principle is a "subtle aura or vapor" which is ' extri- 

 cated from the bowels of the earth." This plague-causing poison was said 

 to affect trees and other plants, fishes and other animals, as well as man. 

 Dr. Mead declared that epidemics were caused by (i) diseased persons, (2) 

 goods imported from infected places, and (3) a vitiated or poisoned state of 

 the air, notions which may be considered as the direct forerunners of the 

 germ theory of disease. 



Let us now go back and consider the ancient ideas regarding spontane- 

 ous generation. Anaximander, of Miletus, who lived during the forty- 

 third Olympiad (610 B. C); believed that many animals developed de novo, 

 from moisture and water acted upon by sun and warmth. The extremist. 



7n 



Pig. 1. — From'the Arcana Natura of A. van Leeuwenhoek. The first published 

 illustration of bacteria. These bacilli of the mouth cavity were seen with the aid of sim- 

 ple lenses only, a, b, bacilli; c, a spirillum; e, perhaps chain forms of bacilli; d, illustrat- 

 ing the characteristic motion of certain bacilli (re to m). 



Empedocles of Agrigentum (450 B. C), declared that all living things upon 

 the/arth were capable of originating spontaneously. Aristotle (384 B . C.) 

 taught that some plants and animals originated spontaneously. Ovid, 

 some three centuries later, gives instructions how to create bees spon- 

 taneously in the carcasses of horses. To within recent times the belief 

 that certain animals could originate spontaneously, that is, without a pre- 

 existing parent, was quite general, and differed only in grotesqueness. 

 Cardan as late as 1542 declared that water created fishes, and that many 

 fermentative processes created animals. Van Helmont gives instructions 

 how to produce mice artificially. Kircher boldly declared that he had 

 seen certain animals develop spontaneously before his eyes. Paracelsus 

 gives instructions how to make homunculi. The instructions are quite 



