376 SPECIAL HISTOLOGY. 



femur, ribs, and the cartilaginous portion of the lamina of the 

 occipital bone. At the end of the second, and beginning of 

 the third month, ossification is apparent in the frontal bone, 

 scapula, bones of the fore-arm and leg, and upper jaw; in the 

 third month, in the rest of the cranial bones, with few excep- 

 tions, the metacarpal and metatarsal bones, and phalanges ; in 

 the fourth month, in the ilium and ossicula auditus ; in the 

 fourth or fifth mouth in the ethmoid, the turbinated bones, the 

 sternum, pubis and ischium ; in the sixth to the seventh month, 

 in the os calcis and astragalus ; in the eighth month, in the 

 os hyoides. At birth, the epiphyses of all the cylindrical bones 

 are still unossified, with the occasional exception of those at 

 the lower extremity of the femur and upper end of the tibia ; 

 and besides these all the carpal and the five smaller tarsal 

 bones, the patella, sesamoid bones, and the last segment of the 

 coccyx. After birth, up to the fourth year, the nuclei of these 

 bones also make their appearance ; but, in the os pisiforme, 

 not till the twelfth year. The union of most of the epiphyses 

 and processes with the diaphyses takes place, in part at the 

 time of puberty, in part towards the end of the period of 

 growth.] l 



1 [Dr. Sharpey's discovery that certain bones of the skull are developed in the 

 same manner as those layers which are formed under the periosteum in the long 

 bones, has been a sort of apple of discord among histologists, and has produced a 

 great variety of controversies not only among them, but among comparative 

 anatomists ; controversies whose heat has been somewhat increased, as we think, by 

 a want of perception among the combatants, of the fact, that several totally distinct 

 questions are involved. These questions seem to us to be the following, and we shall 

 endeavour to consider them in detail. 



1. Whether the tissue from which "secondary" bone proceeds is cartilage, or not ? 



2. Whether it is morphologically homologous with cartilage, or not ? 



3. Whether ossification takes place in it in the same manner as in cartilage, or 

 not? 



And as the result of the answering these : — 4. Whether the differences between 

 the two tissues are sufficient to constitute the basis of a classification of the bones, 

 or not ? 



1. To answer this by saying with Meyer that every tissue which ossifies is carti- 

 lage, is simply to beg the whole question. Cartilage we hold to be distinguished 

 from indifferent tissue, by the fact of its matrix containing chondral. The substance 

 which in the foetus contains no choiulrin, but will subsequently become a cartilage — 

 though in common parlance it is very convenient to call it "foetal cartilage" — is no 

 more cartilage than the cartilaginous basis of a future bone, which might just as pro- 

 perly be called fcetal bone, is osseous tissue. There can be no question then, we 



