PROFESSOR TYND ALL'S RECENT RESEARCHES. 695 



dy. It belonged to the beef-group, and it was a whole day in ad- 

 vance of all the other tubes. The progress of putrefaction was first 

 registered on the 26th of October, The map then taken may be thus 

 described : 



Hay. Of the thirty specimens exposed, one had become " muddy " 

 the seventh in the middle row reckoning from the side of the tray 

 nearest the stove. Six tubes remained perfectly clear between this 

 muddy one and the stove, proving that difierences of warmth may be 

 overridden by other causes. Every one of the other tubes containing 

 the hay-infusion showed spots of mould upon the clear liquid. 



Turnip. Four of the thirty-five tubes were very muddy, two of 

 them being in the row next the stove, one four rows distant, and the 

 remaining one seven rows away. Besides these, six tubes had be- 

 come " clouded." There was no mould on any of the tubes. 



eef. One tube of the thirty-five was quite muddy, in the sev- 

 enth row from the stove. There were three cloudy tubes, while seven 

 of them bore spots of mould. 



As a general rule, organic infusions exposed to the air during the 

 autumn remained for two days or more perfectly clear. Doubtless, 

 from the first, germs fell into them, but they required time to be 

 hatched. This period of clearness may be called the " period of 

 latency," and, indeed, it exactly corresponds with what is understood 

 by this term in medicine. Toward the end of the period of latency, 

 the fall into a state of disease is comparatively sudden ; the infusion 

 passing from perfect clearness to cloudiness more or less dense in a 

 few hours. 



Thus the tube placed in Mr. Darwin's possession was clear at 8.30 

 A. M. on the 19th of October, and cloudy at 4.30 p. m. Seven hours, 

 moreover, after the first record of our tray of tubes, a marked 

 change had occurred. It may be thus described : Instead of one, 

 eight of the tubes containing hay-infusion had fallen into uniform 

 muddiness. Twenty of these had produced bacterial slime, which 

 had fallen to the bottom, every tube containing the slime being cov- 

 ered by mould. Three tubes only remained clear, but with mould 

 upon their surfaces. The muddy turnip-tubes had increased from 

 four to ten ; seven tubes were clouded, while eighteen of them re- 

 mained clear, with here and there a speck of mould on the surface. 

 Of the beef, six were cloudy, and one thickly muddy, while spots of 

 mould had formed on the majority of the remaining tubes. Fifteen 

 hours subsequent to this observation viz., on the morning of the 

 27th of October all the tubes containing hay-infusion were smitten, 

 though in diiferent degrees, some of them being much more turbid 

 than others. Of the turnip-tubes, three only remained unsmitten, 

 and two of these had mould upon their surfaces. Only one of the 

 thirty-five beef -infusions remained intact. A change of occupancy, 

 moreover, had occurred in the tube which first gave way. Its muddi- 



