ANATOMY OF VEETEBEATES. 19 



CHAPTER II. 



OSSEOUS SYSTEM OP HyEMATOCRYA. 



§ 10. Composition of bone. — The vertebrate organisation will 

 be first described as manifested in the great cold-blooded scries, 

 under the diverse modifications, and progressive stages, indicated 

 by the characters of the foregoing sulxlivisions of the class. 

 But lieflire entering upon the details of the osseous system, some 

 observations must be premised on the vertebrate skeleton in general. 



The original substance of all animals consists of a fluid with 

 granules and cells. In the course of developement tubular tracts 

 are formed, some of which become filled with ' neurine ' or nervous 

 matter ; others with ' myonine ' or muscular matter ; other portions 

 are converted into vessels, glands, &c. ; but a great proportion 

 of suljstance, akin to primordial, remains as ' cellular tissue.' 

 This, as a rule, Ijccomes hardened in certain parts of the body of 

 vertebrates by earthy salts, chiefly phosphate of lime. Thus 

 the tissues called ' osteine ' or bone, and ' dentine ' or tooth, 

 are constituted ; between which the chief distinction lies in the 

 mode of arrangement of the earthy particles, in relation to the 

 maintenance of a more or less free circulation of the nutrient 

 juices through such hardened or calcified bodies. 



Fishes have the smallest proportion, birds the largest propor- 

 tion, of the earthy matter in their Ijoncs. The animal or soft 

 part in all is chiefly a gelatinous substance. 



PROPORTIONS OF EARTHY OR HARD,! AND OF ANIMAL OE SOFT, MATTER IN 

 THE BONES OF THE VERTEBRATE ANISIALS. 



FISHES. 



Salmon Carp Cod 



Soft ... 60-62 40-40 34-30 



Hard. . . . 39-38 69-60 05-70 



100-00 10000 10000 



1 This has been termed inorganic ; but that tlio combination of phosphorus and 

 calcium has ever taken place in nature save under the influences of a living organism, 

 remains to be proved. 



c 2 



