264 FUNCTIONS OF THE NERVOUS SYSTEM. 



with the reflex actions, and the other with the consensual, the existence in 

 Articulata seems to be clearly established by Mr. Newport's researches 

 ( 326) ; and although the distinction between the afferent and motor fibres, 

 of each system respectively, has not here been clearly made out, there can be 

 no reasonable doubt of its existence. 



336. The class of consensual actions evidently becomes more predominant, 

 in proportion as the special sensory organs are more evolved, and as the 

 ganglia in immediate connection with them (and altogether forming the cephalic 

 mass) present an increase in their proportionate development. This is 

 especially the case in the higher Arliculata ; in which the Instinctive group of 

 actions attains its highest perfection and predominance. The propriety of 

 referring these to the consensual group, will be obvious upon a little considera- 

 tion. They are as evidently prompted by particular sensations, as are the 

 reflex actions by particular impressions; and the respondence is as uniform 

 in the one case, as in the other. Although in these movements, there is a 

 most remarkable adaptation of means to ends, (as in the construction of 

 habitations by various Insects, and especially by the social Hymenoptera,) 

 yet few persons will maintain that this adaptation is performed by the reason 

 of the animal; since, on this supposition, every Bee solves a problem which 

 has afforded scope for the laborious inquiries of the acutest human mathe- 

 matician.* The adaptation is in the original construction of a nervous system, 

 which should occasion particular movements to be performed under the in- 

 fluence of particular sensations; and the constancy with which these are 

 performed by different individuals of the same species, when placed in the 

 same conditions, leads at once to the belief, that they must be independent of 

 any operations so variable as those of judgment and voluntary exertion. 



337. On the other hand, in the Vertebrata, we shall find the purely reflex 

 and consensual movements forming a smaller proportion of their actions, and 

 brought under a more complete subjection to the Volitional system. This is 

 evident, from the greater variety which the actions exhibit ; from the mode in 

 which they are adapted to peculiar circumstances ; from the degree in which 

 they may be modified by education ; and from various other indications of a 

 superior kind of Intelligence. At last, in adult Man, we perceive that all the 

 movements, which are elsewhere involuntary, but which are not immediately 

 requisite (as are those of deglutition, respiration, &c.) for the maintenance of 



* The hexagonal form of the cell is the one in which the greatest strength, and the nearest 

 approach to the cylindrical cavity required for containing the larva, are attained, with tin; 

 least expenditure of material. But the instinct which directs the Bees in the construction 

 of the partition that forms the bottom or end of the cell, is of a nature still more wonderful 

 than that which governs its general shape. The bottom of each cell rests upon three parti- 

 tions of cells upon the opposite side of the comb; so that it is rendered much stronger, than 

 if it merely separated the cavities of two cells opposed to one another. The partition is not 

 a single plane surface; but is formed by the union of three rhomboidal planes, uniting in the 

 centre of each cell. The angles ibrnied by the sides of these rhombs, were determined by 

 the measurements of Maraldi to be 109 yS' and 72 32'; and these have been shown, by 

 mathematical calculation, to be pwiscly the angles, at which the greatest strength and capa- 

 city can be attained, with the least expenditure of wax. The solution of the problem was 

 lirst atiempted by Koenig, a pupil of the celebrated Bernouilli; and as his result proved to 

 differ lioin the observed angle by only two minutes of a degree, it was presumed that the 

 discrepancy was due to an error of observation, which it was easy to account for by the 

 finallness of the surfaces whose inclination had to be measured. The question has been 

 since taken up, however, by Lord lin Hicham (Appendix to his Illustrated edition of Paley's 

 Natural Theology) ; wlio has worked it out afresh, and has shown that, when certain small 

 quantities, neglected by Koenig, are properly introduced into the calculation, the result is 

 exactly accordant with observation, the Ikes being thus proved to be riglit, and the Mathe- 

 matician 'wrong. 





