IV. CARTILAGE. 



Dissect out the tip of the delicate xiphisternal cartilage of a fresh 

 frog, or slice a bit of the cartilage from the head of the femur with 

 a razor; mount in salt solution and study under the high power. 

 Note : ( i ) Large rounded cartilage cells scattered through a nearly 

 invisible and structureless matrix which forms a refractive halo 

 about each cell. (2) A distinct nucleus (or two) in each cell. (3) 

 After some time the cells contract and thus a space is formed be- 

 tween the cell and the matrix. Draiv. 



* 



V. BONE. 



Examine with low power a section of bone (mammalian bone). 

 Observe: ( i ) Havcrsian canals, rounded spaces often rilled with air 

 or dirt and then appearing black. (2) Lamellae, concentric layers 

 about each haversian canal. (3) Lacunae, oval black spaces be- 

 tween the lamellae. (4) Canaliculi, minute dark lines radiating 

 from the lacunae. (5) Other lamellae are to be found not arranged 

 about canals, but filling in spaces not occupied by such systems. 

 Draw. 



VI. CONNECTIVE TISSUE. 



a. White fibrous tissue : ( i ) Tease out a bit of fresh tendon in 

 water ; with a high power it is seen to be made up of fine wavy 

 fibres in bundles ; each fibre has faint outlines and does not branch. 

 (2) Treat with acetic acid; most of the fibres become invisible, but 

 a few (yellow elastic fibres) and some elongated granular con- 

 nective tissue cells remain visible. 



b. Yellow elastic fibres : Tease out in acetic acid some of the 

 tissue immediately under the frog's skin. Under a high power note : 

 Branched fibres with well defined outlines ; these may not be found 

 until several specimens have been examined. Draw both white and 

 yellow fibres. 



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