THERMAL DEATH-POINT OF LIVING MATTER, 



701 



objects experimented with were thus estimated, and the temperature 

 in successive trials was mostly made to differ from that last employed 

 by 5° R. Operating in this way, and, in the case of eggs or seeds, 

 subsequently taking great care to place those used in the different 

 trials under similar conditions, alike favorable for germination or de- 

 velopment, Spallanzani obtained the following results : 



Of frogs' eggs only an extremely small number developed after hav- 

 ing been simply raised to the temperature of 131° Fahr., while not one 

 developed which had been heated to 145° or upward. Tadpoles pro- 

 duced from similar eggs all perished at 111°, and the same tempera- 

 ture likewise proved fatal to the parent frogs from which the eggs had 

 been derived, as well as to aquatic salamanders and to fish with which 

 experiments were made. 



Silk-worms' eggs, and the eggs of the elm-moth (Papillon de I'Orme), 

 developed less and less frequently when successive batches were heated 

 to temperatures approaching 144|^°. When they were actually sub- 

 mitted to this heat, all perished, though the highest temperature fol- 

 lowed by development is not recorded. Silk-worms themselves, as 

 well as the caterpillars of the elm -moth, were uniformly killed as soon 

 as the water in which they were immersed attained 108^°. 



Eggs of the common blow-fly only developed in very small num- 

 bers when raised to the temperature of 135°, while all perished at 140°. 

 The larvoe developed from these eggs all died, as those of the silk- 

 worm and elm-moth had done, as soon as the temperature of the water 

 rose to 108^°. Other adult larvje, of the same species with which ex- 

 periment was subsequently made, perished at the same heat. 



In addition, Spallanzani experimented with some aquatic organ- 

 isms, though he was unable to discover, and therefore to experiment 

 with, their eggs. Thus leeches perished at 111°, and the Nematoids 

 known as " vinegar-eels" at 113°. Other aquatic worms were killed 

 at 111°, while water-fleas died at 107°. 



So far, therefore, Spallanzani's results were most uniform ; the dif- 

 ferent kinds of eggs were killed by mere momentary exposure to a 

 temperature of about 140° Fahr., while the animals to which they were 

 related perished at or about 110°. 



The abbe next turned his attention to the power possessed by 

 plants and their seeds of resisting the action of heated water. These 

 observations were conducted in the same manner, though only the 

 roots of the plants were immersed in the water while it was being 

 heated. The plants were afterward carefully replaced in earth. Much 

 care was taken when the seeds were sown to keep the batches distinct 

 from one another, and to place them as much as possible under the in- 

 fluence of similar conditions. 



Spallanzani's first experiments were made with the seeds of the 

 chick-pea, lentil, wheat-grass, flax, and clover. The water was heated 

 slowly, and the seeds were taken out as soon as the desired tempera- 



