340 SPECIAL HISTOLOGY. 



the ossicula auditus and the hyoid bone ; but it also presents 

 some cartilaginous portions, which never become ossified, either 

 remaining in the cartilaginous condition during life, or after- 

 wards disappearing ; as for instance, Meckel's process, two 

 cartilaginous lamellae below the nasal bones, a narrow cartila- 

 ginous band connecting the styloid process with the os hyoides, 

 and two others, one of which extends from the outer part of 

 the ala parva laterally to the lamina cribrosa, whilst the 

 other stretches upwards and forwards from the cartilaginous, 

 mastoid and petrous portions of the temporal bone. Conse- 

 quently, in the cartilaginous cranium of man, the vault of the 

 skull is totally wanting, and almost all the lateral portions, as 

 well as nearly all of what afterwards becomes the facial bones : 

 nevertheless, at all events in the true cranium, the parts not 

 formed of cartilage are closed by a fibrous membrane, represent- 

 ing in fact the further development of the soft, primordial, 

 cranial capsule, so that the cranium at this time, though only 

 in part cartilaginous, is yet fully as complete as at an earlier 

 period, and always corresponds to its original soft rudimental 

 form. In other Mammalia, as for instance, in the Pig, the 

 cranium is much more completely cartilaginous (' Mikroskop. 

 Anatomy/ tab. iii, figs. 4, 5.) 



[The complete development of the primordial cartilage, con- 

 sidered histologically , has not yet been accurately traced in all 

 its stages, either in man or in the mammalia. If we wish, 

 therefore, to obtain anything like a sufficient idea of it, we 

 must at present have recourse in a great measure to the lower 

 Vertebrata. If the cartilage of the spinal column and of the 

 head be examined in the batrachian larva, it is readily seen, that 

 they are invariably constituted, while still in the soft state, of 

 the same formative cells with vitelline corpuscles, as all the 

 other organs. Before the development of the external branchiae, 

 these cartilage-cells present the form of closely approximated 

 spherical cells, O007" to 0009'" in size, with nuclei measuring 

 00045 — 0006", and filled with the well-known vitelline cor- 

 puscles ; afterwards, when the branchiae have made their appear- 

 ance, the granular contents of the cells begin to disappear, from 

 within to without, whilst the nuclei become more distinct, lying 

 in a clear fluid within them, and at the same time the cells slowly 



