MUSCULAR SYSTEM. 



531 



regards their means of relation with the external 

 world. Having as yet no ganglia developed 

 sufficiently important, from their size or situa- 

 tion, to merit the title of brains, or fit to be 

 regarded as constituting a common sensorium, 

 whereunto information derived from remote 

 parts of the body may be conveyed, localized 

 instruments of sensation would be as yet super- 

 fluous, and consequently, with the exception 

 of the generally diffused sense of touch which, 

 from its extreme delicacy, seems in these 

 lowest forms of existence to supply to a 

 certain extent the deficiency of other means of 

 perception, instruments of sensation are not 

 as yet conferred. The presence of a localized 

 organ of sense, analogous to an eye or an ear, 

 must obviously be useless to a creature pos- 

 sessed of no sensorial centre, to which informa- 

 tion, derived through the medium of that sense, 

 may be transmitted, and organs of the higher 

 senses are, therefore, as yet entirely wanting 

 throughout the NEMATONEUROSE division of 

 the animal kingdom,* as, a fortiori, they are 

 necessarily deficient throughout the ACRITE 

 classes. In like manner the existence of 

 external locomotive members, moved by any 

 powerful or elaborately constructed muscular 

 apparatus, is not to be expected in animals that 

 possess not ganglia capable of presiding over 

 voluntary muscular motion. Limbs, there- 

 fore, properly so called, are not as yet de- 

 veloped ; and, if in some of the most perfect 

 Epizoa, the rudiments of such structures be- 

 come apparent, it is only because the animals 

 possessing them are so nearly allied to the 

 Articulata, in their general structure, that the 

 nervous ganglia in them are beginning to be 

 developed, and thus they can only be looked 

 upon as the transition steps leading by an 

 almost imperceptible gradation from one great 

 type of animal organism to another of a more 

 elevated character. 



In the ARTICULATA (HOMOGANGLIATA, 

 Owen), brains, or ruling ganglionic centres, for 

 the first time make their appearance in a suffi- 

 cient state of development to correspond with 

 organs of sense of a localized character, or to 

 animate systems of muscles adapted to wield 

 locomotive limbs, and combine complex ac- 

 tions now essentially connected with the more 

 perfect attributes bestowed on forms of life 

 capable of more extensive relations with sur- 

 rounding objects. Still, however, an exact 

 correspondence exists between the progressive 

 expansion of the nervous centres and the gradual 



* In laying this down as an important physiolo- 

 gical axiom, a few words of explanation will be 

 required by those, who, adopting Ehrenberg's 

 views, regard the red spots observable vipon nume- 

 rous Animalcules and Zoophytes as being the eyes 

 of those creatures. That many species of such 

 animals possess red spots occupying definite posi- 

 tions upon different parts of their bodies, no one 

 will be disposed to deny who has paid the slightest 

 attention to their economy and organization ; but 

 that these red spots are eyes, we think, for the 

 reasons above stated, may reasonably be doubted, 

 more especially as it has not even been proved by 

 observation or experiment that they possess either 

 the structure, or the functions of any visvial appa- 

 ratus, with which we are acquainted. 



appearance of limbs moved by a distinct mus- 

 cular apparatus, which become progressively 

 superadded to the annulose body or trunk of 

 the articulated animal, and in precisely the 

 same manner does the advancement of the 

 nervous system from a less perfect to a more 

 concentrated condition evidently precede the 

 appearance of external appendages, subservient 

 to the exercise of more exalted powers of sen- 

 sation, or increased capabilities of locomotion. 

 The humblestannulose forms, as for example the 

 Leech and the Earthworm, possessing, as they 

 do, a nervous system consisting of an extended 

 series of numerous pairs of feeble ganglia, none 

 of which are as yet sufficiently potent to con- 

 trol any complex muscular apparatus, or to 

 appreciate impressions derived from without with 

 muchnicety or precision, are necessarily deprived 

 of outward limbs, or complicated instruments 

 of sense ; their soft and flexible integument is 

 unequal to sustain any jointed members what- 

 ever, and the first rude vestiges of simple eyes, 

 ocelli, are all that can be allowed for the pur- 

 poses of vision. By degrees the nervous gan- 

 glia becoming fewer in number as they coalesce 

 into larger and proportionately more energetic 

 masses, the moving organs of the body become 

 perfected in the same ratio; limbs, almost 

 impotent as yet, but still sketching out the arti- 

 culated legs hereafter to be perfected, make their 

 appearance, and the apodous Annelidan, the 

 humble inhabitant of the water, is promoted 

 to a terrestrial existence ; jointed feet at length 

 become appended to the segments of the still 

 worm-like body, small and feeble at first, as in 

 the lulus terrcstris and the other vegetable- 

 eating MYRIAPODS, but speedily, in proportion 

 as the individual segments of the body become 

 enlarged and strengthened, and the motor gan- 

 glia acquire increased energy, assuming larger 

 dimensions and greater perfection of structure, 

 until the annulose animal attains the strength 

 and activity of the carnivorous Scolopcndra, 

 and becomes fitted for a life of rapine and 

 destruction. 



Advancing from the Scolopendra, which as 

 yet is only able to creep upon the surface of 

 the ground, we are at length conducted to the 

 far more active and highly gifted races of 

 INSECTS, properly so called, in which the de- 

 velopment and perfection of the muscular sys- 

 tem is advanced to a condition adapting these 

 wonderful little beings to an aerial existence, 

 and in making the transition from Myriapod 

 to the Insect the carrying out of the same 

 great law is most obviously and conspicuously 

 illustrated. The nervous ganglia, still nume- 

 rous and proportionately feeble even in the 

 Scolopendru, become in the aerial insect reduced 

 in number until they are collected into a few 

 large and potent masses ; senses of a wonder- 

 fully exalted description, correspondent with 

 the increased size of the encephalic ganglia, 

 replace the simpler organs of the less exalted 

 Articulata ; those segments of the body where- 

 unto locomotive members are appended coalesce 

 and become fused together into a dense and 

 strong thoracic armour able to sustain the vio- 

 lent efforts of the powerful muscles now re- 



2 M 2 



