ZOOLOGY. 281 



peculiar change, either in lessening or quickening the flow of blood 

 from one extremity to the other, but must result solely from the quie- 

 tude of the senses, and from electrical incidents externally. Cabanis, in 

 his Rapports du Physique et Moral, has observed in man that some of the 

 members and senses go to sleep sooner than others. He assigns the 

 soporific influence sensationally to fatigue. The part first feels drowsy 

 in which the flow of the blood is affected. Among the senses, the eye is 

 the first that goes to sleep ; after it the smell, taste, hearing, and touch 

 become successively drowsy. The touch is never entirely insensitive. 

 The sight is more difficult to awaken than the hearing ; a slight noise 

 will rouse a sleep-walker who had suffered light upon his unshut eyes 

 without any apparent influence ; but insects, if affected at all internally, 

 are very little affected in this way. 



The insect world are acutely acted upon by atmospheric circumstan- 

 ces. Rain or cloudy weather operates upon them like a continuance 

 or recurrence of night. It is not the warmth or the dryness of the air, 

 its humid state or its coldness ; it is the electrical condition that affects 

 them. The constant alternations of sleep and waking, in whatever 

 way they may be induced by repose, or affected by functional activity, 

 are regulated as periodical recurrences by the electrical laws of the 

 seasons, by the reiteration of day and night, by the daily variations of 

 the barometer, and by the conditions that move the magnetic needle 

 from east to west at stated hours every day. Extreme weariness will 

 prevent sleep if fatigue is unaccompanied by powerless attention, and un- 

 settled sensation. Let us see how these known facts may serve to ex- 

 plain the sleep of insects. 



"We shall comprehend some of the physiological incidents of slumber 

 by attending to the processes of mesmeric sleep, as developed by Mr. 

 Braid in his work on Neurypnology, or the rationale of nervous sleep, 

 in relation with animal magnetism. I would be brief with my extract, 

 and yet I can scarcely venture to abridge his language. He says he 

 induced cataleptic sleep, which he designates hypnotism, by keeping 

 the eyes fixed on an object, and the mind riveted on the idea of that 

 one object. He so regulated the distance of it from the sight as to 

 produce the greatest possible strain upon the eyes and eyelids. " It 

 will be observed," he says, " that, owing to the consensual adjustment 

 of the eyes, the pupils will be. at first contracted ; they will shortly be- 

 gin to dilate ; and after they have done so to a considerable extent, 

 and have assumed a wavy motion, the eyes will close involuntarily, with 

 perceptible vibrations. Ten or fifteen minutes elapse, and the arms 

 and legs are found disposed to be retained in the position in which 

 they are placed. If the patient has not been so intensely affected as 

 this implies, then, if he be spoken to in a soft tone of voice, and desired 

 to retain the limbs in that, or in an extended position, the pulse will 

 bpeedily become greatly accelerated, and the limbs involuntarily fixed. It 

 will now be found that all the organs of special sense, excepting sight, in- 

 cluding heat and cold, and muscujar motion and resistance, and certain 

 mental faculties, are at first prodigiously exalted. It is such an exalta- 

 tion as happens with regard to the primary effects of opium, wine, and 

 spirits. After a certain point, however, this exaltation of function is 

 folkwed by a state of depression far greater than the torpor of natural 

 sleep. From the state of the most profound torpor of the organs of 

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