118 FORMATION OF SHELLS OF ANIMALS, ETC., 
sary to remove it from the animal. It is preserved in 
glycerine. a, is a piece of cartilage with nodulat edpor- 
tions of earthy matter evidently formed upon it by the 
coalescence of previously existing particles of various sizes, 
but inclining to a rounded figure; 4, these nodulated 
portions still further coalescing to form osseous rings. 
These rings are, in this subject, formed upon a cartilagi- 
nous sternum, and have been exposed by merely stripping 
off the skin. They have no definite relation to the car- 
tilage-cells beneath, nor is there any appearance of the 
phosphate being deposited in their interior, or confined to 
Fig. 7. 
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the intercellular substance around them. These rings 
neither correspond in number nor in form with the car- 
tilage-cells. Their long axes may be coimcident or at 
right angles. Indeed, there is nothing which agrees with 
the notion that the development of the one is in any way 
connected with that of the other. These osseous particles 
simply coalesce upon it as they do upon tendon, or upon 
membrane where no such cells have ever existed. Hence 
the use of cartilage in this and similar situations, is with- 
out doubt simply to serve as a temporary substitute for 
