THE BEGINNINGS OF LIFE. 375 



to repeat his experiments, using precisely the same pre- 

 cautions as before, and yet the results were quite 

 different organisms were now found in his solutions. 

 There was one important difference, it is true. In 

 these latter experiments, M. Pasteur had made use of 

 milk. Now the quantity of organic matter contained 

 in milk is, of course, very great ; it is a highly nutritive 

 and complex fluid. It might, therefore, and ought, per- 

 haps, to have suggested itself to M. Pasteur that the 

 different results of his later experiments were possibly 

 explicable on the supposition that the restrictive con- 

 ditions the boiling of the solution, and the closed 

 vessel already containing air were too potent to be 

 overcome by the organic matter in the one solution, 

 whilst they were not too potent, and could not prevent 

 fermentative changes taking place in that of the other. 



urine, for instance judged by these qualities, may be disagreeably 

 putrescible, though its evolutional tendencies may be quite low. By 

 many experimenters this difference has not been appreciated, and they 

 seem to imagine that in employing urine they make use of a fluid which 

 is very favourable for such experiments forgetting, apparently, that urine 

 is an effete product containing comparatively stable compounds, which 

 have already done their work in the body. It may after a short time 

 swarm with Bacteria, and these may be followed by fungi ; but there is 

 no comparison even as to the actual quantity of these organisms, that 

 may be developed in equal amounts of milk and urine respectively 

 when both are exposed to the air for the same time in similarly- 

 shaped vessels, and under the same bell-jar. The milk soon becomes 

 actually solid with fungus growths. M. Pasteur's '1'eau de levdre 

 sucree,' by his own confession (loc. cit. note, p. 58), is never found to 

 contain any of the higher ciliated infusoria, and though it produces 

 fungi, they are met with in much smaller quantity than in an equal bulk 

 of milk under similar conditions. 



