202 THE ORGANS 



Lymphatics with distinct walls are present in the outer layer 

 of the periosteum. Cleft-like lymph capillaries lined with endothe- 

 lium accompany the blood-vessels in Volkmann's and in the Haver- 

 sian canals. The laciincB and canaliculi constitute a complete sys- 

 tem of lymph channels which communicate with the lymphatics of 

 the periosteum, of Volkmann's and the Haversian canals, and of 

 the bone-marrow. 



Nerves. — Both medullated and non-medullated nerves accom- 

 pany the vessels from the periosteum through Volkmann's canals, 

 into the Haversian canals and marrow cavities. Pacinian bodies 

 (page 439) occur in the periosteum. Of nerve endings in osseous 

 tissue and in marrow little defmite is known. 



TECHNIC 



(i) Decalcified Bone. — Fix a small piece of the shaft of one of the long bones 

 — human or animal — in formalin-Miiller's fluid (technic 6, p. 7) and decalcify 

 in hydrochloric or nitric acid solution (page 10). After decalcifying, wash until 

 all traces of acid are removed, in normal saline solution to which a little ammonia 

 has been added. Dehydrate, and embed in celloidin. Transverse and longi- 

 tudinal sections are made through the shaft, including periosteum and edge of 

 marrow cavity. Stain with haematoxylin-eosin (technic i, p. 20) and mount in 

 eosin-gylcerin. 



(2) Hard Bone. — Transverse and longitudinal sections of undecalcified bone 

 may be prepared as in technic i, p. 106. 



(3) Spongy Bone. — This may be studied in the sections of decalcified bone, 

 technic (i), where it is found near the marrow cavity. Or spongy bone from the 

 head of one of the long bones or from the centre of a short bone may be prepared 

 as in technic (2). 



(4) Red Marrpw. — Split longitudinally the femur of a child or young ani- 

 mal, and carefully remove the cylinder of marrow. Fix in formalin-Miiller's 

 fluid and harden in graded alcohols. Cut sections as thin as possible, stain 

 with haematoxylin-eosin, and mount in balsam. 



(5) Marrow: fresh specimen. — By means of forceps or a vice, squeeze out a 

 drop of marrow from a young bone, place on the centre of a mounting slide, 

 cover and examine it immediately. 



(6) Place a similar drop of marrow on a cover-glass and cover with a second 

 cover-glass. Press the covers gently together, slide apart and fix the specimen 

 by immersion for five minutes in saturated aqueous solution of mercuric chlorid. 

 Wash thoroughly, stain with hasmatoxylin-eosin, and mount in balsam. 



Development of Bone 



KlThe forms -of bones are first laid down eithel-'ih cartilage or in embryonic 

 connective tissue. 'J'he bonc^ of the trunk, extremities, and parts of the bones 



