102 THE FLOATING-MATTER OF THE AIR. 



They had doubtless all given way some days before 

 the 22nd, but I had not taken the precaution to look at 

 them. 



Thus, then, the first two days produced no visible 

 change in the pheasant-infusion, while in two of the 

 hare-tubes putrefaction had vigorously set in. Three 

 days' exposure caused only one of the pheasant-tubes to 

 yield ; four of the hare- infusion had yielded in the same 

 time. The difference between them was also illustrated 

 by the mould upon their surfaces. Some days after 

 their exposure four of the five pheasant-tubes were 

 thickly covered with Penicillium, while the five hare- 

 tubes, with one exception, which could hardly be con- 

 sidered such, had repelled that enemy, maintaining their 

 Bacteria undisturbed. 



Still the deportment of the hare-infusion may have 

 been due, not to any specific difference between hare 

 and pheasant, but to the circumstances preceding death. 

 The researches of Dr. Brown-Sequard show that even the 

 same animal tissue exhibits, under different circum- 

 stances, very different tendencies to putrefaction. In 

 guinea-pigs subjected immediately after death to the 

 action of the magneto-electric current, he found the 

 rapidity of putrefaction to correspond with the violence 

 of the tetanization. He also draws attention to the 



