Prof. W. Preyer on Anabiosis. 505 



however, " in this completely hard frozen condition they 

 were thawed at the fire, they returned to life again," even 

 after thirty-six hours. 



Apart from all statements of others, my experiments alone 

 prove the fact that a frog either deprived of its brain or 

 uninjured, after the whole of its vital processes have been 

 completely suspended owing to the formation of ice in its 

 juices, can go on living after thawing as if nothing had 

 happened. It has not yet been determined how long the total 

 suspension of all vital processes at an internal temperature of, 

 say, — 1° C. may continue without the potential life being 

 destroyed. With regard to plants, it was demonstrated by 

 Julius Sachs (1865) that many can survive freezing, while 

 Prillieux showed that water may solidify in the interior of 

 plants without the destruction of tissues at a temperature of 

 — 2° to —3° C. On the other hand, we do not possess many 

 observations on pelagic animals. The partial destruction of 

 tissue by ice-crystals, observed by Romanes (1877) in a 

 number of Medusse which were frozen hard through and 

 through did not prevent anabiosis on thawing ; but precisely 

 on account of this destruction of tissue the rhythm of the 

 contractions was not the same as before. It is highly 

 probable that in Amphibia also the structure of the contractile 

 substance, of the protoplasm in the muscle-fibres, is perma- 

 nently injured if the lowering of temperature is carried too 

 far ; it was doubtless in consequence of this that the subjects 

 of my experiments, when the internal temperature had sunk 

 below — 2°'5 C, did not recover on being thawed, while this 

 internal temperature itself was fatal to many. But already 

 before this the continuity of all parts of the body was severed 

 by the formation of ice, and consequently the possibility of 

 metabolism was excluded as completely as if the animal had 

 been petrified. This therefore is the crucial test, and not the 

 attainment of the lowest possible temperature and the utmost 

 degree of hardness, which entails the destruction of tissues. 

 Thus much we learn from microscopical examination at the 

 temperature which admits of the detection of ice between 

 the plastic elements of the body. 



II. The Revivification of Desiccated Animals. 



If we allow Tardigrades (Macrobiotics, Echiniscus) or 

 Rotifers to dry up in complete isolation on a slide (tracing a 

 little ring round the body, which is now shrunken past 

 recognition, to facilitate its speedy rediscovery in case the 

 slide is not allowed to remain upon the stage of the micro- 



