359 



name Vibrio. These two kinds of movement are not to be 

 confounded. They must be explained as due to very different 

 causes ; and it seems to me that it is a confusion of these two 

 which is at the bottom of the mistakes made in the assertions 

 as to the survival of Bacteria, &c., after the application of 

 very high temperatures. I have made experiments Avith this 

 matter in view. I boiled a solution containing living Bac- 

 teria for two hours. On searching for them after this, I found 

 them unchanged in most respects, but somewhat firmer in 

 texture, like salt beef on board ship after it is boiled. 

 When treated with chromic acid, iodine, or strong alcohol, 

 the Bacteria remain. Their life is undoubtedly destroyed by 

 these reagents. Every one admits that; but there they 

 remain with but a slight change of appearance. Do what 

 you will, however, they retain their trembling movement; 

 and this is a very misleading phenomenon. Dr. Bastian was 

 good enough to unseal a ilask in my presence, Avhich had 

 been closed at a temperature of 150° Centigrade; and t saw 

 there and then Bacteria exhibiting these active, trembling 

 movements, which, had they come from any other solution, I 

 should have then considered as a proof of their being alive. 

 But with regard totheother kind of movements, it is quiteother- 

 wise. On raising the liquid in which they are to the boiling- 

 point, it stops at once, or if you add any of the reagents just 

 now mentioned. The first kind of movement is no doubt 

 the Brownian movement, first shown by Robert Brown to be 

 exhibited by minute particles of a variety of substances, when 

 placed in liquid. When you have a rod instead of a granule, 

 vibration must act unequally, and hence come the curious, 

 oscillatory, rotating movements of the elongate Bacteria. 

 This discrimination is of the utmost importance. I cannot be 

 certain about other persons, but I am of opinion that ob- 

 servers who have supposed they have found Bacteria sur- 

 viving after boiling have made the mistake which I should 

 have done at one time, and, in fact, have confused the 

 Brownian movements with true living movements. So, 

 according to my notion, a fluid full of Bacteria, moving like 

 Vibriones, and twisting about in various ways, does not 

 necessarily contain anything alive at all. 



How do these Bacteria come about ? I speak with caution, 

 in accordance with experiments by other persons, especially 

 that excellent lady, the Frau Johanna Luders.^ I have never 

 examined yeast without finding Bacteria, and in a sessile 

 state. You may see Bacteria sculling about, and then be- 

 coming quiet, and stuck all about in a perfectly motionless 

 ^ See this Journalj vol. viii. 



