TISSUES OF THE BODY. 249 



tissue. The particles of chondrigenous substance are probably decomposed and ab- 

 sorbed, while new albuminous material is separated from the circulation and trans- 

 formed into collagen just as in connective-tissue. 2. Jtees (London and Edinburgh Phil. 

 Mag. 1838) arranged the following series in relation to the matter in question (but 

 possibly based on insufficient research) temporal bone, humerus, femur, radius, ulna, 

 fibula, tibia, ilium clavicle, ribs, vertebrae, metatarsus, sternum, and scapula. Bibra 

 found, however, a different sequence. 



144. 



Owing to their hardness and solidity, the bones are peculiarly well 

 adapted for the mechanical construction of the body, excelling by a great 

 deal cartilage in this respect. They serve to protect internal organs, and 

 form systems of levers to be worked by the muscles. 



By the deposit of bony earths the flexible bone cartilage is rendered 

 hard, in order to bear the weight of the body without bending. There 

 remains at the same time, however, a certain amount of elasticity and 

 cohesion, which enables osseous tissues to withstand very strong blows, 

 &c., without any breach of continuity. An increase in the proportion of 

 mineral constituents gradually imparts to bone a greater brittleness and 

 fragility. This may be very clearly seen in the difference between the 

 bone of infants and that of very old individuals in a normal state, while 

 in pathological conditions it may be more strongly marked. 



The bones take part also, to a great extent, in the chemical occurrences 

 of the organism, owing to the lively interchange of matter going on in 

 them. And though this is as yet but imperfectly known, both as to its 

 amount and direction, still most physiological facts compel us to regard 

 it as by no means inconsiderable, though subject to great rise and fall. 

 Among these facts relative to the energy of the processes going on in 

 bony tissue may be mentioned the whole vegetative life of the same, the 

 frequent regeneration of its substance, the healing of fractures, &c. The 

 well-known experiment of placing a metal ring round a bone in a young 

 animal, which is found at a later period to be imbedded in the interior, 

 teaches us also the great transformations going on in bony tissue, for which, 

 however, the best proof is to be found in the mode of development of the 

 latter. Moreover, there is not necessarily any destruction of tissue bound up 

 with this interchange of material. The rapid coming and going of matter 

 may be also demonstrated chemically. It is easy to conceive that where 

 there is such abundance of phosphate of calcium, a deficiency in the supply 

 of this salt will result in an inadequate hardening of the bone (Chossat). 

 On the other hand, the well-known experiments of feeding with madder 

 have lost in recent times in scientific significance ; for only the new osseous 

 tissue formed during the absorption of the red colouring matter (i.e., 

 the most external ground lamella under the periosteum, as well as the 

 internal layer of the medullary canals) become coloured (Lieberkuhn, 

 Kodliker}. 



The so wondrously complicated system of canaliculi and lacunae has 

 been looked upon by some as a physiological apparatus presiding over 

 this energetic interchange of material, as a system of vessels for the plasma, 

 which receives with its minute openings nutritive fluids from the exuda- 

 tions of the blood-vessels of the medullary canals and surfaces of the 

 bone, conducting them through the whole tissue, so that every smallest 

 part of the ground-substance participates in the transmission of nutritive 

 matter, organic as well as inorganic (Goodsir, Lessing, Virchow). The 

 circulation, however, of a nutritive fluid through this system of canals, so 

 frequently interrupted by the bone-cells, appears questionable, at the same 



