30 nervocs system; sense of touch. 



subdivisions of matter a< certain porti' >ns of the nervous system do. Tims when it is stated 

 for the fir*t time in our hearing, that the eye of the common house-fly is compounded of 

 no less than 4000 single eyes, it seems impossible that a nerve, originally microscopic, can 



- ibdivided into threads or fibres sufficiently fine to furnish a nerve to each simple eye; 

 and when we an' farther informed that the eye of the dragon-fly has (24,000) six times 

 as many subdivisions as that of the house-fly, our faith is still more severely taxed ; but 

 to suppose that a filament is wanting in an eye, is to suppose that the eye is made in vain ; 

 for the eye depends upon its nervous filament, however slender that maybe, for its power 

 of vision. 



The sympathetic system of nerves in insects has been known from the days of Swam- 

 merdam, who first discovered it in the rhinoceros beetle. While this system is found more 

 or less perfect in all articulated animals, it is specially perfected in insects. The imperfec- 

 tion of the nervous apparatus consists in the absence of the cerebral masses, or of all that 

 portion concerned in the formation of idea>. Nothing appears in the nervous system of 

 the artieulata, higher or above the ganglionic centres which connect together the double 

 ventral chord. The ganglia of this system which are more particularly devoted to the 

 purely animal functions, undergo a slight change during the passage from the larval state 

 to that of the perfect insect ; the change consisting chiefly in a concentration of nervous 

 matter upon those ganglia which are subservient to the function of locomotion. The sym- 

 pathetic system, however, undergoes no change : it is equally perfect in the larva as in 

 the mature animal, and reaches its full development in this early stage of existence, there- 

 by showing that it presides over the functions of vegetative life. 



It i< scarcely necessary to speak more particularly of the functions of the nervous 

 -ystem. It may, however, be observed, that it is upon this system that sensation depends, 

 and the nervous fibrils are the channels through which the properties of external bodies 

 become known to the individual. If we may judge of causes by effects, we are warranted 

 in believing that impressions are received by insects from without, in the same manner as 

 is the case with the higher animals ; and that they possess all those special senses which 

 belong to the latter, and some of them in much greater perfection. 



TorcH. The sense of touch in insects, in consequence of the hard covering of their 

 bodies, must be confined to certain parts. Those who have watched their motions are fully- 

 convinced that the palpi are the organs in which this sense is concentrated, or in which it 

 exists in its greatest perfection. These organs are constantly applied by the insect, after 

 the manner of feelers, to the external bodies with which it comes in proximity ; and they 

 are well adapted by their structure to fulfil such a purpose, being flexible, and furnished 

 with a soft and delicate integument. 



