644 OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



act ( 423) } and the same may be said of the acts of coughing and sneezing 

 ( 555), the purpose of which is most obvious, and the adaptation to that pur- 

 pose most complete, yet these acts are most assuredly not performed with any 

 notion of their purpose, but at the prompting of an irresistible impulse, which, 

 originating in an excitation applied to a sensory surface and conveyed to the au- 

 tomatic centres, becomes the immediate source of all the separate muscular con- 

 tractions which combine to accomplish the prearranged result. 1 



676. Thus, then, the type of psychical perfection among Invertebrated ani- 

 mals, which is manifested in the highest degree in the Social Insects, consists in 

 the exclusive development of the Automatic powers; in virtue of which, each 

 individual performs those actions to which it is directly prompted by the im- 

 pulses arising out of impressions made upon its afferent nerves, without any 

 self-control or self-direction ; so that it must be regarded as entirely a creature 

 of necessity, performing its instrumental part in the economy of Nature from 

 no design or will of its own, but in accordance with the plan originally devised 

 by its Creator. On turning to the Vertebrated series, on the other hand, we 

 find that perfection consists in the highest development of the Intelligence, and 

 in the supreme domination of the Will, to which all the automatic movements, 

 save those which are absolutely essential to the maintenance of the organic 

 functions, are brought under subjection ; so that each individual becomes an 

 independent, self-moving, and self-controlling agent, all whose actions are per- 

 formed with a definite purpose which is distinctly before his own view, and are 

 adapted to the attainment of their end by his own reason. This, however, is 

 only true of Man in his highest state of psychical development ; for not only 

 do the actions of the lower Vertebrata appear to be nearly as much under tho 

 direction of automatic impulses as are those of the Invertebrated classes, but 

 the same is true of those of the Human species in infancy and early childhood ; 

 and a very close correspondence may be traced between the gradual develop- 

 ment of the Intelligence and the progressive acquirement of Volitional domi- 

 nance, in the ascending series of Vertebrated animals, and in the advance of 

 Man from the mental state of childhood (which is permanently retained, as to 

 all its essential characters, in many adults, and even in whole races of the least 

 cultivated order) to the highest elevation which his nature is capable of display- 

 ing in his present sphere of existence. The superaddition of these more ele- 

 vated psychical endowments is coincident with the addition of a peculiar gan- 

 glionic centre, the Cerebrum, to the automatic apparatus of Vertebrated ani- 

 mals ; and the relative proportion which this bears to the automatic centres, 

 both as to size and complexity of structure, corresponds so closely with the 

 degree of predominance which the Intelligence and Will possess over the In- 

 stinctive propensities, that it is scarcely possible to doubt that the Cerebrum is 

 the instrument through which these higher psychical powers are exercised. Even 

 in Man, however, the Automatic division of the Nervous system still constitutes 



1 We have not, perhaps, any right to affirm that there is nothing whatever analogous in 

 the Invertebrata to the Reasoning powers and Will of higher animals; but if these 

 faculties have any existence among them, they must be regarded as in a merely rudiment- 

 ary state, corresponding with the undeveloped condition of the Cerebrum. In none of 

 the Articulata has any trace of this organ been discovered ; a rudiment of it, however, 

 has been supposed to exist in the Cuttle-fish. The only distinct indication of intelligence 

 displayed by Invertebrata is the slight degree of capacity of "learning by experience" 

 which some of them display ; this capacity being limited to the mere formation of asso- 

 ciations between the mental states called up by different objects of sense, which we observe 

 to be the first stage in the development of the mental powers in the Human infant. And 

 it is interesting to remark that this educability is less displayed by Insects, in which we 

 may consider the Automatic tendencies as attaining their highest development, than it is 

 in Spiders, which present in several points of their conformation an approximation to wards 

 the Vertebrated series. 



