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FIFTEEN FIGURES INTRODUCTIONThe contrasting patterns of the blood vessels in the red and white muscles were first studied by Ranvier (1874). He chose the semitendinosus and adductor magnus muscles of the rabbit as representatives of the red and white muscles respectively. He found the vascular disposition in the white muscle t o be of the classical type with rectangular meshes of the capillaries, while in the red muscle he found that the longitudinal capillaries were tortuous and that the transverse connections between them and venules presented sac-like dilatations. His histological studies of the structural differences between the red and white muscles were in agreement with the findings of Claude Bernard and Ray Lankester (1871) on the functional differences between these two types of muscle. Meyer (1875) extended and confirmed Ranvier's observations, whose work has since then been commonly cited in standard textbooks of anatomy and histology.In the next four decades, the vascular patterns in the muscle received less attention than the histology and chemistry of the contractile elements of red and white muscles (P e t r h , '36 ; P e t r h , Sjostrand and S y l v h , '36 ; Smith and Giovacchini, '51 ; Heroux and Pierre, '57). It was with the intention of re-examining the vascular patterns of red and white muscles from the morphological standpoint that the present investigation was carried out. MATERIAL Ah'D METHODSThe muscles were obtained from seventeen domestic rabbits of both sexes ranging in age from one month to two years and ten months. The red muscles (Craigie, '51) used were semitendinosus, soleus and tenuissimus (tensor fasciae cruris, Kerr, '55), and the white muscles used were adductor magnus, semimeinbranosus and gastrocnemius.The muscles from one adult rabbit were prepared for paraffin sections for a general histological study of muscle fibers and the intramuscular blood vessels. Another adult rabbit was injected with colored latex at a pressure of 240 mm Hg and then dissected for the purpose of tracing the source and distribution of the main vessels. The remaining rabbits were injected, under ether or chloroform anethesia, through the abdominal aorta after being perfused with warm saline with either 10% Higgin's India ink or 1.6% Prussian blue in 10% gelatin solution at 38°C. The pressure was kept constant during each injection, and ranged in multiples of the average blood pressure of the rabbit, 120 mm Hg (Doniinguez, '27; Rai, '31 ; Koch and Koller, '32), namely, 240 mm Hg, 360 mm Hg, 480 mm H g o r 600 mm Hg. The muscles of one of the ink-injected rabbits were treated with 3% KOH and rendered transparent in glycerin for the study of the patterns of vascular ramification. The gelatin-injected rabbits were treated by Ranvier's (1874) method, and the muscles of one of them were minutely dissected under a binocular microscope. VASCULAR PATTERNS I N MUSCLES 599Muscles for microscopic study were prepared for serial sections by the usual paraffin and celloidin methods. The fixatives used were 10% for...

SYNOPSIS In muscle fibres of the gastrocnemius of adult rabbits and rats, denervated for at least one month, electron microscopy revealed peculiar lamellated structures. Some of these appeared as arrays of parallel double lamellæ; others folded themselves into ovoids or asterisk‐like patterns, while still others were of irregular shape. One to three months after denervation, the outer membrane of many muscle nuclei protruded to a varying extent, and later the protrusion folded into an array of parallel double lamellæ. When the array reached a certain size, it became detached from the nuclear membrane and assumed various forms. Such structures were more numerous in muscles denervated for longer than 3 months. They seemed to move gradually toward the sarcolemma and to become finally attached to it or to fuse with it. These findings support the current view that all membrane‐bounded cytoplasmic organelles belong to a common “membrane system” extending from the plasma membrane to the nuclear membrane. It is concluded that the lamellated structures in denervated muscle are derived from the outer nuclear membrane and that they are an outcome of the degeneration of muscle nuclei.