382 



We have just seen, that the drought and heat 

 of the Llanos act like cold upon animals and 

 plants. Beyond the tropics the trees lose their 

 leaves in a very dry air. Reptiles, particularly 

 crocodiles and boas, having very indolent habits, 

 leave with difficulty the basins where they have 

 found water at the period of great inundations. 

 In proportion as the pools become dry, these 

 animals penetrate into the mud, in search of the 

 degree of humidity that gives flexibility to their 

 skin and integuments. In this state of repose they 

 are seized with stupefaction : but they preserve a 

 communication perhaps with the external air; 

 and, however little this communication is, it 

 may suffice to keep up the respiration of an ani- 

 mal of the saurien family, provided with enor- 

 mous pulmonary bags, exerting no muscular mo- 

 tion, and in which almost all the vital functions 

 are suspended *. It is probable, that the mean 

 temperature of the dried mud, exposed to the 

 solar rays, is more than 40°. When the North 

 of Egypt, where the coolest -§* month does not 

 fall below 13*4°, still sustained crocodiles, they 

 were often found torpid with cold. They were 

 subject to a winter sleep, like our frogs, our 



* See my experiments on the respiration of young croco- 

 diles in the Obs. de Zoologie, vol. i, p. 258. 



f This is the mean temperature of the month of February 

 at- Cairo, lat. 30° 2' : toward Thebes the diminution of the 

 temperature is naturally less, 



