124 ON THE VERTEBRATE SKULL. 



are called " lateral masses of the Ethmoid." or " superior 

 and middle spongy bones," and more immediately by the per- 

 forated cribriform plate, which allows of the passage of the 

 filaments of the olfactory nerve, and connects these lateral 

 masses with the lamina perjpenclicularis, or proper ethmoid. 

 Looking at the bones which form the immediate walls of the 

 upper and middle part of the nasal chambers, with reference 

 only to the olfactory organs, we might say, in fact, that the 

 anterior vacuity of the cranium proper is stopped by the 

 ossified walls of the olfactory sacs, consisting of the ethmoid 

 and vomer in the middle line, of the superior and middle 

 spongy bones (or so-called lateral masses of the ethmoid) 

 supero-laterally, of the inferior turbinal bones infero-laterally. 

 And to these ossifications must be added, as members of the 

 olfactory group, the bones of Bertin, posteriorly and superiorly, 

 and the nasal bones, anteriorly and superiorly. 



The great posterior vacuity on each side is filled up by the 

 Temporal hone, which consists of a very considerable number of 

 distinct elements, only distinguishable by dissection and by 

 the study of development in Man, but which remain perma- 

 nently distinct, and undergo very strange metamorphoses in 

 many of the lower Vertebrates. Some of these constituents 

 of the temporal bone, such as the squamous portion or Squa- 

 mosal (Sq.), and the Malleus, Incus, and Stapes, are discrimi- 

 nated by the student of ordinary human anatomy ; but there 

 are many others which he is not in the hab't of regarding as dis- 

 tinct osseous elements. r lhus the bony ''external auditory 

 meatus" is primitively a distinct bone, termed Tympanic (Ty.) 

 on account of its affording the frame in which almost the whole 

 of the tympanic membrane is set. The Styloid process (St.) 

 is originally a distinct bone. And, lastly, the pars petrosa and 

 pars mastoidea of human anatomy are, in reality, made up of 

 three distinct ossifications, of which I shall have to say more 

 presently, but which I shall speak of for the present under the 

 collective name of the Periotic bones, because they immediately 

 surround the organ of hearing:. 



Not merely the periotic, but also the squamosal and tym- 

 panic bones are so closely related to the auditory organ, that 



