110 Insect Vision and Insect Sleejo. 



or the rationale of nervous sleep, in relation with animal mag- 

 netism. 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 rivetted 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 begin 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 vibra- 

 tions. 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 speedily become greatly accelerated, and 

 the limbs involuntarily fixed. It will now be found that all the 

 organs of special sense, excepting sight, including heat and 

 cold, and muscular motion and resistance, and certain mental 

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

 altation as happens with regard to the primary effects of opium, 

 wine, and spirits. After a certain point, however, this exalta- 

 tion of function is followed 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 special sense and tonic rigidity 

 of the muscles, they may at this stage be instantly restored to 

 the opposite condition of extreme mobility and exalted sensi- 

 bility, by directing a current of air against the organ or organs 

 we wish to render limber, and which had been in the catalepti- 

 form state. By mere repose the senses will speedily merge 

 into the original condition again." Now, none of these pro- 

 cesses, in inducing sleep, would be apphcable to insects whose 

 eyes are immoveable, if the provision for seeing was confined to 

 the two large globular eyes on each side of the head ; but being 

 provided with ocelli, or auxiliary eyes, placed on the vertex of 

 the head, these facts illustrate the drowsy insect. The struc- 

 ture of these auxiliary organs is just that of one of the lenses 

 of the compound eye, but being so placed that they can bo set 

 close to what they examine, and can concentrate the attention 

 to the exclusion of the objects that occupy the globular facetted 

 eyes, it is possible that such visual concentration, when the 

 insect retires to repose, induces just that perceptive vibration 

 described in cataleptic sleep by which slumber can be brought on. 

 An insect composes itself to sleep with its antenna; folded. 

 Some of the beetles adjust them to their breast ; the butterfly 



