222 M. Flourens on Hibernation, 



The author then spoke of the external circumstances which 

 induce torpidity. Cold, at least in our climates, is the first con- 

 dition, to which is to be joined the deficiency of excitement on 

 the part of the external agents. It has been said that hght pre- 

 vents torpidity, and the same has been said of food. The ex- 

 periments made by M. Flourens have demonstrated to him that 

 the influence of these two causes (at least in the lerot) is either 

 nuU, or very limited. 



I come now, continued the author, to the internal or organic 

 conditions. It will be perceived of how much importance it is 

 first to determine upon what organ or what organic modification 

 lethargy depends, and, in the second place, what is the mechanism 

 of this phenomenon. Now, on these two points, science possesses 

 as yet nothing but conjectures ; and, with respect to the first, 

 there is scarcely any organ to which these conjectures have not 

 been directed. But the two organs which have figured most in 

 this respect, are the brain and the thymus gland : the brain, to 

 which physiologists have long been in the habit of referring all 

 that they could not otherwise explain ; and the thymus, a glan- 

 dular body, situated on the fore part of the body, penetrating 

 into the thorax, and on which the mode of its development 

 seemed to confer peculiar rights to perform the chief part in 

 torpidity. In fact, this organ is in the highest degree of de- 

 velopment at the moment when the animal becomes lethargic, 

 it shrivels at the period of its awakening ; and, in the other 

 mammifera, it disappears almost entirely in adult age, and is 

 only developed in the fcetus, whose state in the uterus approaches 

 in many respects to that of the lethargic animal. 



These two conjectures required to be subjected to experiment, 

 especially at the present day, when the experimental method 

 has ah'eady localized so many other phenomena, and when, to 

 speak Iiere only of my own experiments on the brain, it has 

 succeeded in determining in it a distinct organ for the sensa- 

 tions, an organ for the locomotory motions, and an organ for 

 the motion of preservation ; and when it has even found a point 

 in it, scarcely a few lines in extent, to which it is suflicient that 

 any given part be attached to enable it to live, from which if it 

 be detached it dies, and which thus constitutes the central and 

 vital point of the economy. 



