532 



NATURE OF REPRODUCTION. 



Fig. 169. 



Schultze's experiment on SPONTA- 

 NEOUS GE NEK AT ION. a. Flask con- 

 taining watery infusion, b. Potash-ap- 

 paratus containing sulphuric acid c. 

 Potash-apparatus containing caustic po- 

 tassa. 



potash-apparatus (b, c), similar to those used for condensing carbonic 

 acid in organic analyses. One of these (b) was filled with concen- 

 trated sulphuric acid, the other (c) with a solution of caustic potassa. 



The flask with the organic infusion 

 having been subjected to a boiling 

 temperature, in order to destroy any 

 living germs which it might con- 

 tain, the stopper was inserted, and 

 the whole apparatus exposed to the 

 light, at the ordinary summer tempera- 

 ture. The connections of the apparatus 

 being perfectly tight, no air could pene- 

 trate into the flask, except by passing 

 through either the sulphuric acid or 

 the potassa; either of which would 

 retain and destroy any organic germs 

 which might be suspended in it. Every 

 day a fresh supply of air was introduced 

 into the flask by drawing it through 



the tubes b, c ; and in this way the atmospheric air above the infu- 

 sion was constantly renewed, while at the same time the introduction 

 of living germs from without was effectually prevented. 



Schultze kept this apparatus under his observation, as above, from 

 the last of May till the first of August ; frequently examining the 

 edges of the fluid with a lens, through the sides of the glass jar, 

 but without ever detecting in it any traces of living organisms. At 

 the end of that period the flask was opened, and the fluid which it 

 contained subjected to direct examination, equally without result. 

 It was then exposed, in the same vessel and in the same situation 

 as before, to the free access of the atmosphere, and at the end of 

 two or three days it was found to be swarming with infusoria. 



It is plain, therefore, that the infusoria cannot be regarded as 

 produced by spontaneous generation, but must be considered as 

 originating in the usual manner from germs; since they do not 

 make their appearance in the watery infusion, when the accidental 

 introduction of germs from without has been effectually prevented. 



ANIMAL AND VEGETABLE PARASITES. This very remarkable 

 group of organized bodies is distinguished by the fact that they 

 live either upon the surface or in the interior of other animal or 

 vegetable organisms. Thus, the mistletoe fixes itself on the branches 



