MUSCULAR TISSUE. 53 



ceeds towards the circumference. In the long bones, there is a central point 

 of ossification for the shaft or diaphysis; and one or more for each extremity, 

 the epiphyses. That for the shaft is the first to appear; those for the extremi- 

 ties appear later. The union of the epiphyses with the shaft takes place in the 

 inverse order to that in which their ossification began; for, although ossification 

 commences latest in those epiphyses towards which the nutrient artery in the 

 several bones is directed, they become joined to the diaphyses sooner than the 

 epiphyses at the opposite extremity, with the exception of the fibula, the lower 

 end of which commences to ossify at an earlier period than the upper end, but, 

 nevertheless, is joined to the shaft earliest. 



The order in which the epiphyses become united to the shaft, appears to be 

 regulated by the direction of the nutrient artery of the bone. Thus the arteries 

 of the bones of the arm and forearm are directed towards the elbow, and the 

 epiphyses of the bones forming this joint become united to the shaft before 

 those at the opposite extremity. In the lower extremities, on the contrary, the 

 nutrient arteries pass in a direction from the knee; that is, upwards in the 

 femur, downwards in the tibia and fibula; and in them it is observed, that the 

 upper epiphysis of the femur, arid the lower epiphyses of the tibia and fibula, 

 become first united to the shaft. 



Where there is only one epiphysis, the medullary artery is directed towards 

 that end of the bone where there is no additional centre: as, towards the acro- 

 rnial end in the clavicle; towards the distal end of the metacarpal bone of the 

 thumb and great toe; and towards the proximal end of the other metacarpal 

 and rnetatarsal bones. 



Besides these epiphyses for the articular ends, there are others (more com- 

 monly called apophyses) for projecting parts, or processes, which are formed 

 separately from the bulk of the bone. For an account of these the reader must 

 be referred to the descriptions of the individual bones in the sequel. 



A knowledge of the exact periods when the epiphyses become joined to the 

 shaft, is often of great importance in medico-legal inquiries. It also aids the 

 surgeon in the diagnosis of many of the injuries to which the joints are liable; 

 for it not unfrequently happens, that on the application of severe force to a 

 joint, the epiphyses 'become separated from the shaft, and such injuries may be 

 mistaken for fracture or dislocation. 



MUSCULAK TISSUE. 



The Muscles are formed of bundles of reddish fibres, endowed with the pro- 

 perty of contractility. Two kinds of muscular tissue are found in the animal 

 body, viz., that of voluntary or animal life, and that of involuntary or organic 

 life. 



The Muscles of Animal Life (striped muscles) are capable of being put in 

 action and controlled by the will. They are composed of bundles of fibres 

 inclosed in a delicate web of areolar tissue, called in the figure the "perimy- 

 siurn." Each bundle consists of numerous smaller bundles, inclosed in a 

 similar fibro-areolar covering, and these again of primitive fasciculi. 



The fibres are of no great length not extending, it is said, further than an 

 inch and a half. They end either by blending with the tendon or aponeurosis, 

 or else by becoming drawn out into a tapering extremity which is connected 

 to the neighboring fibre by means of the sarcolemrna. The precise mode in 

 which the muscular fibre joins the tendon has been variously described by 

 different observers. It may, perhaps, be sufficient here to say that the sarco- 

 lemma, or membranous investment of the muscular fibre, appears to become 

 blended with the tissue of the tendon, and that the muscular fibre appears to 

 be prolonged more or less into the tendon, so that the latter forms a kind 

 of sheath around the fibre for a longer or shorter distance. When muscular 



