ANATOMY OF VEKTEBEATES. 19 



CHAPTER II. 



OSSEOUS SYSTEM OP H^EMATOCRYA. 



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

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

 under the diverse modifications, and progressive stages, indicated 

 by the characters of the foregoing subdivisions of the class. 

 But before 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 substance, akin to primordial, remains as l cellular tissue.' 

 This, as a rule, becomes 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 bones. The animal or soft 

 part in all is chiefly a gelatinous substance. 



PROPORTIONS OF EARTHY OR HARD, 1 AND OF ANIMAL OR SOFT, MATTER IN 

 THE BONES OF THE VERTEBRATE ANIMALS. 



100-00 100-00 10000 



1 This has been termed inorganic ; but that the 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 



