. The comparative anatomy of the domesticated animals. Veterinary anatomy. B, ULTIMATE FIBRIL OF MUSCLE (according TO BOWMAN). C, Muscular fibre more highly magnified, its myolemma being so thin and transparent as to allow the ulti- mate fibrillae to be in the fresh muscles of insects; in the higher animals, this disassociation into parallel fibrillae is generally only possible in muscles subjected to the action of certain reagents. Other reagents favour the breaking up of the fibre into super- posed discs ; hence it has been concluded that the fundamental element of the primitive muscular fib
. The comparative anatomy of the domesticated animals. Veterinary anatomy. B, ULTIMATE FIBRIL OF MUSCLE (according TO BOWMAN). C, Muscular fibre more highly magnified, its myolemma being so thin and transparent as to allow the ulti- mate fibrillae to be in the fresh muscles of insects; in the higher animals, this disassociation into parallel fibrillae is generally only possible in muscles subjected to the action of certain reagents. Other reagents favour the breaking up of the fibre into super- posed discs ; hence it has been concluded that the fundamental element of the primitive muscular fibre was not a fibril, but a discoid segment of fibrillae, to which Bowman gave the name of sarcous elements (Fig. 143). Bowman considered that the transverse striae represent the lines of union of the sarcous elements. But nowadays the striation of the fibre is explained by the striation of the primitive contractile cylinder ; in fact, each of these is divisible into a series of thick, dark- coloured, contractile discs, joined by bright bands which play the part of a tissue framework in the cylinder. In the majority of Mammals, the thick discs are traversed in their middle by a pale streak named the intermediate band or streak of Hensen ; in the middle of each bright band is a thin disc dividing it into two parts. In the Invertebrata the situation is more complicated, as is seen in Fig. 147. Kanvier has remarked that there is, in the Skate and Rabbit, pale and dark striped muscles. The pale muscles are recognized by the predominance of the transverse striation and the rarity of nuclei; wliile the fibres of the dark muscles present, on the contrary, a great number of nuclei and prevailing longitudinal striation. Lavocat and Arloing have examined these difl'erences in the muscular apparatus of some Fishes, Birds (Fowls, Guinea-fowls), and domestic Mammals (Dog, Ox, Horse), and their observations confirm those of Ranvier, apart from some secondary differences special to the varied
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