. Kirkes' handbook of physiology . s are distributed in this membrane, andminute branches from these periosteal vessels enter the Haversian canals MICROSCOPIC STRICTURE OF BONE 43 to supply blood to the solid part of the bone. The long bones are suppliedalso by a proper nutrient artery which, entering at some part of the shaftso as to reach the medullary canal, breaks up into branches for the supplyof the marrow, from which again small vessels are distributed to the interiorof the bone. Other small nutrient vessels pierce the articular extremitiesfor the supply of the cancellous tissue. Micros
. Kirkes' handbook of physiology . s are distributed in this membrane, andminute branches from these periosteal vessels enter the Haversian canals MICROSCOPIC STRICTURE OF BONE 43 to supply blood to the solid part of the bone. The long bones are suppliedalso by a proper nutrient artery which, entering at some part of the shaftso as to reach the medullary canal, breaks up into branches for the supplyof the marrow, from which again small vessels are distributed to the interiorof the bone. Other small nutrient vessels pierce the articular extremitiesfor the supply of the cancellous tissue. Microscopic Structure of Bone. Notwithstanding the differencesof arrangement just mentioned, the structure of all compact bone substanceis found under the microscope to be essentially the same. Examined with a rather high power its substance is found to contain amultitude of small irregular spaces, approximately fusiform in shape, calledlacuna, with very minute canals or canaliculi, as they are termed, leading 1 JIM IP If lip lit. Fig 54.—Longitudinal Section from the Human Ulna, Showing Haversian Canals, Lacuna?, and Canaliculi. (Rollett.) from them, and anastomosing with similar prolongations from other lacunae,figure 53. In very thin layers of bone, no other canals than these may be visi-ble; but on making a transverse section of the compact tissue of a long bone,as the humerus or ulna, the arrangement shown in figure 53 can be bone seems mapped out into small circular districts, at or about thecenter of each of which is a hole, around which are concentric layers, thela mcllaz, the lacuna and canaliculi following the same concentric distributionaround the center, with which indeed they communicate. On making a longitudinal section, the central holes are shown to besimply the cut extremities of small canals which run lengthwise throughthe bone, anastomosing with each other by lateral branches, figure 54, and 44 CELL DIFFERENTIATION AND THE ELEMENTARY TISSUES are c
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