THE ORIGIN AND PROPAGATION OF DISEASE. ,2;3:9 



establish, twenty years ago,* the vegetable nature and structural rela- 

 tions of Bacteria^ and he has recently contributed largely to our knowl- 

 edge of their classification and general physiology.t According to him 

 the putrefaction of nitrogenous organic matters is neither a spontaneous 

 post-mortem decomposition, nor is it a simple oxidation under the influ- 

 ence of the atmosphere. " It is rather a chemical process caused by the 

 action of Bacterium termo. Just as sugar is never converted sponta- 

 neously into alcohol and carbonic acid, and is brought into fermentation 

 only by the yeast-fungus, so nitrogenous organic matters never putrefy 

 of themselves, but only by means of the vital activity and multiplication 

 of Bacteria. * * * We may therefore," he says, " apply Pasteur's doc- 

 trine also to the decomiDosition of animal matters, and may adopt as 

 true the seeming paradox that putrefaction is an incidental phenomenon^ 

 not of death, but of vitality." 



The proof that living Bacteria are the cause of putrefaction, and not 

 merely its accompaniment, is that a putrescible liquid which has been 

 sufficiently boiled and received in a snper-heated glass vessel may be 

 kept in contact with the atmosphere indefinitely without putrefaction, 

 provided the access of Bacteria be prevented by a plug of cotton-wool. 

 But, if the minutest portion of any liquid already infected with Bacteria 

 be added, putrefaction at once begins. Dr. Burdon- Sanderson, by a 

 series of very important experiments in 1871,| has established the fact, 

 which is also confirmed by the researches of Cohn,§ that contamination 

 by the germs of Bacteria takes place, as a general rule, not directlj^ from 

 the atmosphere, but by means of water and unclean moist surfaces ; 

 while, on the other hand, the germs of the mold-fungi, like penicilium 

 and mucor, are more or less constantly present in the air, and so readily 

 gain access to organic substances, even in a dry atmosphere. Conse- 

 quently, such substances, if properly protected against Bacteria, do not 

 putrefy, but, on the other hand, may become covered with a mold-fungus- 

 Dr. Sanderson even cut out the muscular tissue of the thigh of a recently, 

 killed Guinea-pig, and hung it up under a bell-glass, using for this pur- 

 pose a knife and hooks which had just been subjected to the flame of a 

 Bunsen burner, but taking no other precautions 5 and for thirty-one 

 days, though the exposed tissues were overgrown with penicilium, there 

 was no development of Bacteria, and no evidence of putrefaction. 



The natural history of Bacteria is especially connected with the ques- 

 tion of spontaneous generation, because they are the only class of organ- 

 isms now remaining in which reproduction by spores has not yet been 

 discovered, and because they appear so promptlj^ and abundantly in all 

 putrescible liquids under ordinary exposures. 



Whatever may be the difference of opinion, therefore, with regard to 



* "Nova Acta Academise Carolo-Leopoldinie," lib. xxiv, p. 1. 



t "Beitriige zur Biologie der Pflanzen," 1872, No. ii, p. 127. 



t " Thirteenth Report of the Medical Officer of the Privy Coxincil," London, 1871. 



j "Beitriige zur Biologie der Pliauzen," No. ii, p. 189. 



