VII.] BONE, OSSIFICATION, TEETH. 75 



Examiae carefully the thinnest part of the strip 

 (containing fewest lamellae) for the fine decus- 

 sating fibres of the matrix ; add acetic acid, both 

 the perforating and decussating fibres swell up 

 and become indistinct or lost to view. 



B. Ossification. 



1. Cut a longitudinal section through the head of 

 the femur of a newly-born rabbit, cat, etc. The 

 femur -should have been divided longitudinally 

 into four parts, and treated with picric or 

 chromic acid to harden it and to dissolve the 

 salts. Stain the sections with eosin or picro- 

 carmine, wash with water, place first ia dilute 

 and then in strong spirit, clear with creosote and 

 turpentine' (or turpentine alone) and mount in 

 Canada balsam (cp. Lesson IV. footnote). Observe 



a. The normal hyaline cartilage. 



b. The cartilage cells arranged in rows. Note 

 that many of the cells in section are tri- 

 angular, the broad side of one lying above 

 the angle of the other; this indicates an 



^ Tlie creosote and turpentine is used since it dissolves any 

 paraffin that may be attached to the tissue (from the imbedding), 

 makes the tissue tranapairent, and mixes well with the Canada balsam ; 

 carbolic acid may be used instead of the creosote, it is cheaper but 

 does not dissolve the paraffin mixture quite so readily. Clove oil 

 causes less shrinking in many tissues than creosote and turpentine, 

 but it is much dearer than either of them and does not dissolve the 

 paraffin mixture in the cold. The clearing of the sections takes place 

 more readily and certainly if they are placed for a few minutes in 

 absolute alcohol before they are placed in the clearing agent. 



