CHAP. VII.] THE CONNECTIVE TISSUES. 273 



the circle nearest the Haversian canal and the canal itself. The 

 lacunae lodge nucleated masses of protoplasm the bone corpuscles or 

 bone cells which do not send processes into the canaliculi. 



The walls of the calcified lacunae and canaliculi, as well as of 

 the Haversian canals, appear to be composed of a tissue resembling 

 elastic tissue 1 and are left surrounding the bone cells when softened 

 bone is boiled for many hours in water or when it is subjected to 

 digestion with trypsin 2 . 



Besides the lamellae or sheets of bony substance which are 

 arranged in concentric layers around the Haversian canals, and which 

 may be termed the lamellae of the Haversian systems, other lamellae 

 are arranged concentrically around the medullary canal and imme- 

 diately beneath the periosteum ; these may be termed fundamental 

 lamellae. 



The minute structure and arrangement of the soft parts of bone 

 can only be studied by making preparations of decalcified or softened 

 bones. In these preparations it may be shewn that the ultimate 

 lamellae of bone are transparent sheets which exhibit intercrossing 

 fibres, which possess the characters of the white fibres of connective 

 tissue. It may further be shewn that the fundamental lamellae are 

 perforated by fibres the so-called perforating fibres of Sharpey 

 which dip into the bone from the periosteum, and which appear to 

 have mainly the chemical characters of yellow elastic tissue. 



The Water found in Bone. 



All bones contain, when fresh, a considerable quantity of water. 

 The estimates of various observers differ remarkably in reference to 

 this matter. Volkmann estimates the mean percentage of water at 

 48 '6 p.c. of the fresh bone. According to Aeby's determinations 

 (which are certainly 'too low) bones just removed from the dead body 

 contain between 11 and 12 p.c. of water. According to this author 

 the water exists in a state of chemical combination, probably ana- 

 logous to that of water of crystallization. This view is based partly 

 on the constancy of the amount of water, but partly on the fact that 

 heat is evolved when dried bone is placed in water 3 . 



The Animal or Organic basis of Bone. 



Methods of When a bone is placed in a dilute mineral acid for 



preparing de- some days, it gradually loses its rigidity, and although 

 calcified or retaining its form and general appearance, it becomes 

 bone - comparatively soft and pliable, so that a long and com- 

 paratively thin bone, such as the clavicle or the radius, may be tied 

 into a knot. 



1 Hoppe, Virchow's Archiv, Vol. v. (1853) p. 170. 



2 De Burgh Birch, "Erscheinungen bei Trypsinverdauung an Knochen." Central- 

 Matt f.d. med. Wissenschaft. 1879, p. 945. 



3 Aeby, "Der Grund der Unveranderlichkeit der organischen Knochensubstacz." 

 Centralblatt f. d. med. Wissenschaft. 1871, No. 14. 



G. 18 



