534 



MUSCULAR SYSTEM. 



Professor Elirenberg has more recently an- 

 rounced that he had detected a nervous fila- 

 ment encircling the margin of the disc in one 

 cf the pulmonigrade Acalephse, and connecting 

 the red spots, which he is pleased, as we think 

 without sufficient reason, to call eyes, with each 

 other. Such a nervous system would, at least, 

 be anomalous; and, notwithstanding the justly 

 high reputation of the eminent professor of 

 Berlin, we cannot but think that the interests 

 of physiology require us to pause before we 

 assent to the views of Professor Elirenberg, as re- 

 lates to the nature of the h'lament in question. 



In the Sterelinintliu or parenchymatous En- 

 tozoa of Cuvier, the same acrite condition, both 

 of the nervous and muscular systems, is still 

 observable in the lower forms belonging to this 

 group of internal parasites, which being, for the 

 most part, in their natural situations either en- 

 closed in cells or closely imbedded in the sub- 

 stance of the viscera of other animals, could 

 not be expected to have any power of locomo- 

 tion conferred upon them ; their bodies are, 

 therefore, in the simplest species (such as the 

 Hydatids, Cysticerci) mere membranous bags 

 of homogeneous texture, and without a trace 

 of fibre in their composition : their powers of 

 moving are proportionately feeble, and are 

 limited in fact to slight contractions, which are 

 but indistinctly perceptible on the application 

 of stimuli to the surface of the living animal. 



In the Tape-worms ( Teeni<e) the presence 

 either of nerve or muscle is equally impercep- 

 tible, and the whole structure strictly conform- 

 able to the Acrite type. As, however, we 

 mount higher in the scale of organization 

 among these parasites, we again find how 

 nearly succeeding types of structure are made 

 to approximate, and even to a certain extent to 

 become blended, as it were, with each other. 

 In the Flukes (Distoma) and kindred genera, 

 and in many of the Acanthocephalous Sterel- 

 mintha, although their structure is evidently 

 parenchymatous, the skin, without presenting 

 any decided appearance of muscular fibre, be- 

 comes more coriaceous and contractile, and at 

 the same time nervous filaments become dubi- 

 ously perceptible : a transition is obviously in 

 progress, and thus we are gradually introduced 

 to another and a more elevated series of 

 animals. 



The NEMATONEURA, as is obvious from 

 every part of their economy, are gifted with 

 higher attributes, and permitted to enjoy a 

 more extended intercourse with external ob- 

 jects than any creatures comprehended under 

 the preceding division. They are no longer 

 rooted to one spot or imprisoned in enclosed 

 cavities, but, on the contrary, are for the most 

 part erratic in their habits, and in many of them 

 the locomotive system is so efficiently con- 

 structed that their movements, exhibiting con- 

 siderable activity and energy, argue the posses- 

 sion of distinct and precisely arranged muscles, 



searches are well known, that, although they had 

 examined several hundred specimens of the Beroe 

 in question, for the purpose of ascertaining this im- 

 portant fact, their endeavours to detect the nervous 

 svstsm referred to had been entirely unsuccessful. 



and display such combination and consentane- 

 ous action of different purls of the body co- 

 operating to produce a given result, that the 

 existence of an intercommunication throughout 

 the system by means of nerves might readily 

 be predicated, even had not anatomy revealed 

 to us that such animals actually possess a ner- 

 vous apparatus. It would seem indeed to be 

 clearly indicated by the physiological relations 

 that exist between the two systems, that the 

 possession of muscular fibre arranged in dis- 

 tinct fasciculi involves, as a matter of course, 

 the co-existence of nervous threads, whereby 

 the actions of distinct and distant muscles may 

 be associated for the attainment of a common 

 object; and accordingly we find that these two 

 important additions to the animal economy 

 make their appearance simultaneously. No 

 large ganglionic masses are as yet developed of 

 sufficient importance to be regarded as consti- 

 tuting a common sensorium, to which the per- 

 ceptions derived from external senses must be 

 referred, and from whence mandates of volition 

 can be supposed to emanate. Senses, there- 

 fore, that is, localized and special senses, can- 

 not as yet be given ; the traces of individuality 

 are but feebly recognizable ; the vital powers 

 are still, to a great extent, diffused throughout 

 the different tissues of the body, and not col- 

 lected and concentrated, as in animals pos- 

 sessed of brains, that is, of centralized and 

 dominant aggregations of neurine; and, as a 

 consequence of this important circumstance, 

 some of the most striking characters common 

 to the ZOOPHYTES still linger in this division 

 of creation ; the radiated form is yet extensively 

 met with, multiplication by mechanical divi- 

 sion of the body is still, to a certain extent, 

 possible, and severed portions of the body are 

 found to be reproduced by growth from the 

 mutilated part. 



The CCELELMIXTHA or cavitary intestinal 

 worms, living in the interior of other animals, 

 differ in so many points from the Acrite Entozoa, 

 that Cuvier, although in the lli-gne Animal he 

 was content to group th^m together in the same 

 class, was obliged to separate them into two 

 distinct orders, calling the STE HELMINTH A 

 " intestinaux parenchymateux," while the more 

 highly organized are designated " inteatinuux 

 cavitai?-es." The Ccelelmintha, in fact, are or- 

 ganized in accordance with quite a different 

 type of structure, as must be at once evident 

 upon the slightest comparison between them. 

 The digestive apparatus is now no longer com- 

 posed "of tubes excavated out of the general 

 mass of the body, and presenting no outlet for 

 the escape of egesta, but a distinct alimentary 

 canal now makes its appearance, suspended in 

 a capacious abdominal cavity, wherein, more- 

 over, are lodged the male and female organs of 

 generation, which in the Ccelelmintha are gene- 

 rally found in different individuals. The pa- 

 rietes of the body are in these worms obviously 

 muscular, and are composed of contractile 

 fibres arranged in superposed strata and affect- 

 ing different directions. Towards the exterior 

 of the body they are disposed longitudinally, 

 but the inner layers assume a circular or spiral 



