40 EVERS's COMPARATIVE ANATOMY. 



In the mammalia, thick fibro-cartilages appear interposed between 

 the bodies of the vertebras, and in the carnassier and climbing 

 mammalia, the articular processes are furnished with well developed 

 synovial capsules. The tails of many quadrupeds enjoy full motion 

 from their coccygeal vertebras being united by synovial capsules. 

 The anterior and posterior common ligaments of the spine are 

 powerfully strong and highly elastic along the pliant columns of 

 the cetacea. In the large and heavy-headed herbivorous quadru- 

 peds, the ligamentous nuchas is of great size and strength, extending 

 from the occipital protuberance along the cervical and dorsal spines, 

 and in many instances, to the coccygeal and iliac spines. The 

 light-headed, and active muscular carnassier have this ligament 

 short and small, and in the quadrumana and many of the rodentia 

 scarcely a trace of it is to be found. The inter-articular cartilage 

 of the lower jaw is met with, in this, but not in the preceding classes, 

 the ligamentum teres is found in most of this class, but is said to be 

 absent from the ourangs, the elephant, the rhinoceros, the hippopo- 

 tamus, the kangaroo, the sloths, and the monotremata. The two 

 toes of those ruminants, whose habits oblige them to make rapid 

 and bounding movements, are secured by strong transverse liga- 

 ments passing between their phalanges. 



CHAPTER Y. 



ON THE MUSCULAR SYSTEM IN THE INVERTEBRATA. 



General observations. — In the higher orders of animals, there is 

 a close relation, and a perfect mutual dependence between the 

 osseous and the muscular systems; so much so, indeed, that the 

 arrangement of one may be at once inferred by any one who pos- 

 sesses a sufficient acquaintance with the other. It is by means of 

 this system that animals are enabled to move from place to place, to 

 seize, masticate, and swallow their aliment, to circulate their fluids, 

 to expel their excretions, to produce various sounds, and to accom- 

 plish an infinitude of other purposes. A system ordained to execute 

 so many offices cannot fail to present some interesting peculiarities 

 in the animal kingdom. In obedience to a law, often alluded to, 

 we find that the muscles of the highest classes of red-blooded ani- 

 mals, during their development, pass through the soft, colourless, 

 and gelatinous condition of those of the lowest species before they 

 attain the characters peculiar to them in their highest state of 

 development. 



Radlata. — No muscular fibres have been hitherto found in the 

 polygastric animalcules. Their rapid motions through the fluids 

 which they inhabit appear to be accomplished by means of the vibra- 

 tions of minute cilia (which are analogous to the villi on the mucous 

 surface of a small intestine) growing from the outer surface of their 



