44 SPECIAL ANATOMY. 



cell-shaped interspaces (medullary cells) of the spongy substance, 

 and contain a loose, vascular areola tissue with numerous fat cells, 

 the marrow of the bone, medulla ossium. The narrowest, from 

 0.005 to 0'002 of an inch in diameter, lie immediately upon the 

 external surface of the bone. The medullary canals are surround- 

 ed by from four to twelve concentric 



Osseous plates, lamella, which take a wavy course, and are perforated by 

 short fibres, or by rectangular, narrow canaliculi, the calcigerous tubes. Be- 

 tween the lamellae in the homogeneous basement tissue of the osseous car- 

 tilage, clear spots, or corpuscles having dark edges, are disposed; these are the 



Bone corpuscles, lacunae, oval, disc-like cavities, filled with granular matter, 

 from which, in a stellate manner, there pass off on all sides the 



Calcigerous canals, extremely delicate tubules, with numerous ramifications, 

 in which the osseous matter or lime is found as a fine white precipitate. 



Membrane of Bones. The external surface of bones is covered by Perios- 

 teum, and this again by Epithelium, in the cavities of the nose ciliated ; but 

 the articular extremities terminated by cartilage are uncovered, and therefore 

 uneven. Here the medullary canals terminate in blind extremities. 



Internal membrane of Bones, Memb. Medullaris, is nothing but the outer sur- 

 face of the delicate areolar tissue which attaches the medullary matter loosely 

 to the internal surface of the osseous tubes. 



Vessels. In the periosteum a close vascular rete is placed, the fine (arte- 

 rial) ramusculi of which enter the medullary canaliculi by the innumerable 

 openings in the cortical substance, again interlace with one another, and 

 anastomose with the vascular rete of the cavity of the bone or medullary 

 cells. This receives its blood from larger vessels, art. nutritice, one of which 

 enters through a large foramen nutritium about the middle of each (tubular) 

 bone. The first nourish the substance of the bone; the last the medulla. 

 The venous blood is returned partly by vena nutritite which accompany, at 

 least, the large art. nntrit. partly through peculiar canals, which are found in 

 the diploe of the flat bones. From these canals the thin- walled, valveless 

 veins pass out into the periosteum. They cannot be injected from the ar- 

 teries. 



Lymphatics are demonstrated in the medulla, but not yet, with certainty, 

 in bone. 



The existence of nerves is upheld by the sensation accompanying inflam- 

 mation of the medulla. The bone substance itself is without sensation. 



[The periosteum is supplied, plentifully, with nerves. TRANS.] 



43. Development of bone, Osteogenesis. 



In the embryo a solid cartilage at first appears, cartilagofor- 

 mativa, seu ossescens, which consists of a mass of homogeneous 

 cells, in the centre of which are formed the medullary canaliculi, 

 surrounded by capillary vessels. In the parietes of the canaliculi, 

 and in the lamellae, the lacuna?, and calcigerous canaliculi ap- 

 pear, and after that the deposit of lime commences, at first in 

 the cartilaginous substance, next in the canaliculi ; but it is unde- 

 cided whether or not the earthy matter is chemically united with 



