Introduction to A^imi at Morphology. 17 



cells,* which are often polynuclear. This exists in the 

 trachea, the articular ends of bones, &c. Fibro-cartilage has 

 a basis of fibrillar tissue containing cartilage cells : in the 

 embrj'o it begins as hyaline cartilage, but the matrix fibrillates 

 {Raihke and Rabl-Riickhardt). The quantity of retiform 

 fibrous tissue in the matrix is small in the adult laryngeal and 

 costal cartilages, large in cotyloid ligaments, the clavicular 

 articular crusts of Primates, and in interarticular cartilages. 

 Reticular-fibro cartilage, with a basis of elastic tissue, is found 

 in the external ear, the epiglottis, the processus vocalis of the 

 arytenoid cartilages {Rhemer), &c. Calcification takes place 

 in the cartilages of Sharks, &c., by the deposition of lime- 

 salts in the intercellular substance. In Mammals, a layer of 

 calcified cartilage lies at the junction of the ribs and costal 

 cartilages ; (reticular cartilage rarely calcifies). In the deve- 

 lopment of cartilage, nuclei first appear in the protoplasm, 

 these multiply, and the tissue divides into cell areas ; the 

 cells become surrounded by clear margins : at first there is no 

 matrix, but this develops apparently out of successive concen- 

 tric cell-capsules. 



7th. Bone is a form of connective tissue only found in 

 Vertebrates, consisting of corpusclesf united by branched 

 processes, in a matrix containing ossein and lime salts (Phos- 

 phate and Carbonate, with a small quantity of Magnesia, and 

 a trace of Ca Fl). The proportions of animal and earthy 

 matters vary in different species:]: and at different ages.§ The 



* These may be split into laminae by chromic acid. Osmic acid shows 

 the matrix to be traversed by straight striae (juice canals of Buhnoff). 



t Rarely, as in some fishes and in dentine, there are no corpuscles but 

 only branching canaliculi or processes. 



\ The proportions in some animals are : — 



Man, Animal matter = 33 Earthy = 67. Ox, Animal = 3 1 Earthy = 69. 



Lion, ,, ,, = 27 ,, = 72. Salmon, ,, =60 ,, = 40. 



Cod, „ „ = 34 .. = 65- Porpoise, „ =35 „ = 64. 



Frog, ,, ,, =35 ,, =64. Snake, ,, =31 ,, =68. 



This variation shows that bone is a mechanical mixture of these elements. 



By dilute hydrochloric acid we may remove the earthy matter : by burning 



we may remove the animal portion. 



\ The proportions at different ages in Man are — 49 per cent, of animal 



C 



