IOWA ACADEMY OF SCIENCES. 



67 



argued that a period of incubation must occur for each disease, and as wheat seed 

 only produces wheat, so too the particular seniinia of a disease only produces that 

 disease. He too aryued that decomposition is brought about when sown with 

 material, that this material propagates and grows. 



In 1820 Ozanam wrote a learned dissertation on epidemic and epizootic diseases, 

 in which he says it is not neceesary to show that the theories of Plenciz and others 

 are purely hypothetical and erroneous. Notwithstanding that Ozanam doubted 

 the correctness of the view of Plenciz on the contagious nature of diseases, others 

 continued to carefully study the organisms of water, etc. Russworm designated 

 them by their form, and, although he carefully studied them, this subject advanced 

 but little. A host of scientists studied these so-called animals because it afforded 

 great amusement. Little, however, was added till the celebrated Danish investi- 

 gator, Otto Friederich Mueller, of Copenhagen, in 1776, made an exhaustive study 

 of these so called Infusoria. He recognized the great difficulty in the study of these 

 organisms, for he says "the certain and clear distinction of these requires so much 

 time and sharp discrimination with the eyes, as well as excellent judgment and so 

 much evenness of mind and patience that scarcely anything else equals it." He 

 described ten species of the t^erwis Monas and thirty-one of the genus Vibrio. He 

 used such characters as motion, biological characteristics. Morphology and habitat. 

 These germs were accurately figured so that it has been possible to recognize some 

 of the species. But we must rapidly pass in review the work of Paula Schrank, 

 who divided these vibriones into those with motion and motionless. Bory de St. 

 Vincent placed these low forms in the family Vibrionides, deriving some of his 

 characters from Auguillula. He recognized five genera. 



SPONTANEOUS GENERATION. 



The theory of spontaneous generation long held sway in the popular mind. 

 During the middle of the eighteenth century the defenders of this theory pro- 

 mulgated their doctrines and for a long time the field was held undisputed. In 

 this cause were enlisted such men as Needham, who observed the development of 

 living organisms from grains of wheat and barley. 



Although this material had been boiled and heated for a time and the vessel 

 closed, still they dfiveloped. The arguments seemed impregnable and Buffon, and 

 Wrisberg, Treviranus and others dunng the early decades of this animated discus- 

 sion championed the cause of abiogenesis with a great deal of empha^is, During 

 the fifties and sixties and in the seventies and even down in the eighties abiogen- 

 esis has had its defenders in such men as Pouchet, Joly, Musset, Wyman, Mante- 

 gazza, Huizinga, Bastian, and Wigand*. It is strange that the clear and logical 

 thinker Wigand should, as late as 1884, assert that bacteria can arise independ- 

 ently without pre-existing forms from an organic substance e. g. spontaneously. 



This, it seems to me, shows a lack of the proper methods of experimentation. 

 Wigand had scarcely reached the stage of experimental work, where it was left by 

 Spallanzani in 1769, who, as some one has said, was the most celebrated experi- 

 menter of that century. We may also mention Bonnet who was in thorough 

 accord with this celebrated experimenter. With Spallanzani began the system of 

 sterilization and making of tests to set aside spontaneous generation. It led 

 Appert to utilize heat in.the preservation of organic substances and has opened 

 the way for glorious modern achievements. 



Later investigators held that Spallanzani's experiments were not above criticism, 



*Eatstehuns uud Fermentwirkung der Bakterien vorlaufige Mlttheilung, Zwelte 

 Auflage, N. G. Elwertssche Verlagsbuchhadulung, 18S4, pp. 40 Seep. 5. 



