PUTREFACTION AND INFECTION. 101 



§ 24. Developmental Power of Infusions and Solu- 

 tions : Air-germs contrasted with Water-germs. 



Wishing to make no experiment, whether with self- 

 cleansed, filtered, or calcined air, or with infusions with- 

 drawn from air by the air-pump, or contained in 

 hermetically-sealed vessels, without exposing the same 

 infusions to ordinary air, this comparison was instituted 

 with the substances mentioned at pages 96 and 97. 

 One hundred test-tubes, an inch wide and 3 inches 

 deep, were divided into groups, each group being filled 

 with the same infusion. The groups were suflSciently 

 numerous to embrace all the substances mentioned in 

 the Table referred to. Exposed to the uncleansed air, 

 they were attacked with different degrees of rapidity 

 and vigour; but in a few days all of them without 

 exception became muddy and crowded with life. On 

 the whole, the hare- and pheasant-infusions presented 

 the greatest contrast. The tubes containing the former 

 were far gone before those containing the latter were 

 sensibly invaded. The putrescibility of pheasant, more- 

 over, was exceeded by that of snipe, partridge, and 

 plover. The sheep's heart examined was also slow to 

 putrefy. A single illustration of this difiference of 

 developmental power may be given here. 



On the 13th of November thirty tubes, containing 

 infusions of partridge, pheasant, snipe, hare, sheep's 

 heart, and codfish, five tubes being devoted to each, to- 

 gether with four tubes of plover, three of mullet, and 

 three of liver, were exposed to the laboratory air. On 

 the 15th, 16th, and 22nd the numbers taken possession 

 of by Bacteria were as follows : — 



