CHAP. XI. GENERAL SUMMARY. 267 



of meat than they were before. If exposed to a tem- 

 perature of between 115 and 125 (46-l 51-6 Cent.), 

 they are quickly inflected, and their protoplasm under- 

 goes aggregation ; when afterwards placed in cold water, 

 they re-expand. Exposed to 130 (54'4 Cent.), no in- 

 flection immediately occurs, but the leaves are only 

 temporarily paralysed, for on being left in cold water, 

 they often become inflected and afterwards re-expand. 

 In one leaf thus treated, I distinctly saw the protoplasm 

 in movement. In other leaves, treated in the same 

 manner, and then immersed in a solution of carbonate 

 of ammonia, strong aggregation ensued. Leaves placed 

 in cold water, after an exposure to so high a tem- 

 perature as 145 (62'7 Cent.), sometimes become 

 slightly, though slowly, inflected ; and afterwards have 

 the contents of their cells strongly aggregated by car- 

 bonate of ammonia. But the duration of the immer- 

 sion is an important element, for if left in water at 

 145 (62-7 Cent.), or only at 140 (60 Cent.), until it 

 becomes cool, they are killed, and the contents of the 

 glands are rendered white and opaque. This latter 

 result seems to be due to the coagulation of the albu- 

 men, and was almost always caused by even a short 

 exposure to 150 (65'5 Cent.) ; but different leaves, and 

 even the separate cells in the same tentacle, differ con- 

 siderably in their power of resisting heat. Unless the 

 heat has been sufficient to coagulate the albumen, car- 

 bonate of ammonia subsequently induces aggregation. 

 In the fifth chapter, the results of placing drops of 

 various nitrogenous and non-nitrogenous organic fluids 

 on the discs of leaves were given, and it was shown 

 that they detect with almost unerring certainty the 

 presence of nitrogen. A decoction of green peas or 

 of fresh cabbage-leaves acts almost as powerfully as an 

 infusion of raw meat ; whereas an infusion of cabbage- 



