68 SKELETON. 



particulars, which will be pointed out more in detail hereafter. 

 At present it may be stated, that the ends of all the long bones 

 are cartilaginous the carpus and tarsus are nearly in the same 

 state the vertebrae, true and false, have their processes very 

 imperfect; and consist, each, in several distinct pieces, united by 

 the remains of the cartilaginous state. Several of the bones of 

 the head are in the latter condition; and the sutures are so im- 

 perfect that the flat bones readily ride over each other from the 

 thinness of their edges, and also have the angles rounded, which 

 occasions the vacancies called fontanels. 



From the early embryo .state to the completion of the skele- 

 ton, three stages are observable in the progress of ossification; 

 the first is mucous or pulpy, the second cartilaginous, and the 

 third osseous. 



I. The mucous stage is observable at a very early period after 

 the embryo has been received into the womb, and presents 

 itself under two modifications. In the one, from the general 

 softness of the whole structure of the embryo, and from the 

 apparently homogeneous nature of its constituents, the mucous 

 rudiments do not distinguish themselves from the other parts: 

 This condition, however, is soon changed into one, and that be- 

 fore the expiration of the first month of gestation, in which they 

 assume a solidity and colour, which mark them off, both to 

 the eye and to the touch, from the still softer parts surrounding 

 them. 



II. About the expiration of the first month the mucous stage 

 is converted into the cartilaginous, and the consistence of the 

 bones then increases continually by the accumulation of gela- 

 tine. Bichat makes a remark on this subject which has been 

 confirmed by the experiments of Scarpa, though erroneous de- 

 ductions have been made by the latter: that we do not see, 

 during the formation of the cartilages, those longitudinal striae 

 in the long bones, radiated in the flat, and mixed in the thick 

 bones, which distinguish the osseous state. The cartilaginous 

 state presents another peculiarity worthy of observation: all the 

 bones which in a more advanced stage are to be united by carti- 

 lage, as the vertebrae, those of the pelvis, and of the head, make, 



