§ v.] Origin and distribution. 45 



the other hand that it would be an exaggeration to suppose 

 that these bodies are everywhere present, that is, in every 

 minutest space. Even Pasteur's earlier and famous researches 

 show the inequality of the distribution by extreme examples. 

 This may be briefly illustrated by the following account. A 

 small quantity of germ-free nutrient fluid, very favourable for the 

 development of lower organisms, was introduced into small 

 narrow-necked phials of 1-200 ccm. content ; the air was 

 withdrawn from the phials and the narrow neck hermetically 

 closed. Subsequently the closed neck was reopened by in- 

 tentional fracture of its extremity; air rapidly poured in, and 

 as soon as this had taken place the neck was once more closed. 

 From 1-200 ccm. of air were thus hermetically inclosed in the 

 phial. The germs which they contained were at liberty to develope 

 in the nutrient fluid, which, to use a short expression, remains 

 unaltered if no germs are present. Of ten such phials filled with 

 air in the court-yard of the Paris Observatory not one remained 

 unaltered ; nine out of ten filled in the cellar of the Observatory, 

 which was almost entirely free from dust, and nineteen out of 

 twenty filled at the Montanvert near Chamonix were unaltered. 



The views here expressed with regard to the origin of 

 Bacteria, and especially the fundamental axiom, that they are 

 produced without exception from germs springing from species 

 of the same name, have not been arrived at without trouble or 

 without opposition, and the latter has not entirely ceased even 

 at the present day. We must not pass by the view of the 

 opponents without at least a brief consideration. It may be 

 concisely stated thus : Bacteria may be formed at any moment 

 from parts of other organisms, living or dead ; but it is allowed 

 that they may afterwards multiply by their own growth and also 

 produce their own germs. 



This view is a survival from the old doctrine of original 

 production without parents, spontaneous or equivocal genera- 

 tion. Plants or animals are often known to appear in numbers 

 in places where they had never been seen before, and the super- 



