217 



sible surface area of tlie latter ; 3. A high heat coiidiictivity 

 of the warming bath and, in particular, a good contact con- 

 ductivity (as it has been said in the previous section, a 

 liquid bath is far superior in this respect to all others). 



II. LIVING MATTER 



1. General Proeedure. The principle that the solidifica- 

 tion of a liquid into a glass requires less molecular rear- 

 rangement than the transformation of that liquid into a 

 crystal suggests that vitrification might not injure proto- 

 plasm in conditions in which crystallization kills it. 



Our first attempts at vitrifying living matter have con- 

 sisted in applying to it the methods of vitrification and 

 vitrofusion and then testing for its vitality. Only a few 

 experiments, and these on but a few types of material, 

 have been carried out to ascertain whether or not the 

 treated protoplasm had actually been brought into the 

 vitreous state. In the following account, therefore, the 

 vitality of living matter treated by the vitrification meth- 

 ods is taken as indicative of a probability that the material 

 was actually vitrified. Vitality after treatment does not, 

 indeed, constitute a proof of vitrification, but, if masses of 

 protoplasm, of small size and not too high water content, 

 are still alive after rapid cooling and rapid warming, while 

 they are killed in larger quantity, or when they have a 

 higher water content, or when they are cooled or warmed 

 slowly, vitality does afford at least indirect evidence that 

 vitrification has been achieved. 



In as far as living beings are comparable to the gelatin 

 solutions which we studied previously, we can expect to 

 succeed in vitrifying organisms whose thickness is about 

 one third of a mm., if their water content is about 50^/( 

 and smaller organisms of greater water content, provided 

 the latter does not exceed 90 ^c. 



2. Methods. For rapid cooling, we used the method of 

 immersion in liquid air. For rapid warming, we ordi- 

 narily immersed the material in water at a temperature 

 of about 20°. Occasionally we employed water heated to 



