2O Introduction 



ible only so long as there were particles suspended in the at- 

 mosphere to reflect it. When the dust had completely 

 settled and the light ray had become invisible because of 

 the purity of the contained atmosphere, the tubes were 

 cautiously filled with urine, beef -broth, and a variety of 

 animal and vegetable broths, great care being taken that 

 in the manipulation the pipet should not disturb the dust. 

 Their contents were then boiled by submergence in a pan of 

 hot brine placed beneath the chamber, in contact with the 

 projecting ends of the tubes, and subsequently allowed to 

 remain undisturbed for days, weeks, or months. In nearly 

 every case life failed to develop in the infusions after the 

 purity of the atmosphere was established. 



The following extracts from Tyndall's work * will illus- 

 trate how slowly the doctrine of spontaneous generation 

 was abandoned: 



"At a meeting of the Pathological Society of London, 

 held April 6, 1875, the 'germ theory' of disease was formally 

 introduced as a subject for discussion, the debate being 

 continued with great ability and earnestness at subsequent 

 meetings. The conference was attended by many dis- 

 tinguished medical men, some of whom were profoundly 

 influenced by the arguments, and none of whom disputed 

 the facts brought forward against the theory on that occa- 

 sion. 



"The leader of the debate, and the most prominent 

 speaker, was Dr. Bastian, to whom also fell the task of 

 replying on all the questions raised. 



"The coexistence of bacteria and contagious disease 

 was admitted; but, instead of considering these organisms 

 as probably the essence, or an inseparable part of the es- 

 sence, of the contagium, Dr. Bastian contended that they 

 'were pathological products spontaneously generated in the 

 body after it had been rendered diseased by the real contagium. 



"The grouping of the ultimate particles of matter to 

 form living organisms Dr. Bastian considered to be an 

 operation as little requiring the action of antecedent life 

 as their grouping to form any of the less complex chemical 

 compounds." "Such a position must, of course, stand or 

 fall by the evidence which its supporter is able to pro- 

 duce, and accordingly Dr. Bastian appeals to the law and 

 testimony of experiment as demonstrating the soundness 



* Op. dt. 



