484 



MOVEMENTS- VOICE AND SPEECH. 



FIG. 161. Transverse section of bone, from the shaft 

 of the human humerus ; magnified ISO diame- 

 ters (from a photograph taken at the United 

 States Army Medical Museum). 



Marrow of the Bones. The marrow is found in the medullary cavities of 

 the long bones, filling them completely and moulded to all the irregularities 



of their walls. It is also found filling 

 the cells of the spongy portion. In 

 other words, with the exception of 

 the vascular canals, lacuna? and cana- 

 liculi, the marrow fills all the spaces 

 in the fundamental substance. The 

 cavities of the bones are not lined 

 with a membrane corresponding to 

 the periosteum, and the marrow is 

 applied directly to the bony sub- 

 stance. In the foetus and in very 

 young children the marrow is red 

 an d verv vascular. In the adult it is 

 yellow in some bones and gray or 

 gelatiniform in others. It contains 



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connective tissue, blood-vessels and 

 nerves. Robin has described little bodies, existing both in the form of cells 

 and free nuclei, called medullocells. These are found in greater or less num 

 ber in the bones at 

 all ages, but they are 

 more abundant in 

 proportion as the 

 amorphous matter 

 and fat-cells are de- 

 ficient. The nuclei are 

 spherical, sometimes 

 with irregular bor- 

 ders, generally with- 

 out nucleoli, finely 

 granular, and ^^ 

 to -g^g-fr of an inch (5 

 to 8 fji) in diameter. 

 They are insoluble in 

 acetic acid. The cells, 

 which are less abun- 

 dant than the free nu- 

 clei, are spherical or 

 slightly polyhedric, 

 contain a few pale granulations, are rendered pale but are not dissolved 

 by acetic acid, and they measure about y^Vir ^ an ^ ncn (15 /*) m diameter. 

 Irregular, nucleated patches, described by Eobin under the name of myelo- 

 plaxes, more abundant in the spongy portions than in the medullary canals, 



FIG. 162. Bone-corpuscles, with their prolongations (Rollett). 



