Morphology of the Human Lachrymal Bone, fyc. 243 



The contiguous part of the maxilla shows some noteworthy characters 

 in development, scattered bony nuclei appear in the infra-orbital 

 membrane and in the membranous nasal process during the early 

 part of the sixth week, and in skulls of foetuses of 32 millims. long 

 these have coalesced into continuous plates, one behind and below the 

 lachrymal in the floor of the orbit, the other in front and internal, 

 and early continuous with the ossification of the front of the maxilla. 

 The latter arises by several nodules irregularly divided into two sets, 

 one of which forms the crista lachrymalis anterior, the others coalesce 

 to form the rest of the nasal process, but these early unite, and in 

 thirty foetal skulls I have only once seen a distinct trace of a 

 persistent suture between these elements after the end of the third 

 month. There always, however, persists the row of vascular holes 

 along this line becoming the sutura notha of the adult. The infra- 

 orbital nucleus consists at its first appearance of several irregularly 

 elongated bony spicules beneath the infra-orbital nerve. Very 

 rapidly, however, as these coalesce and extend forwards towards the 

 brim of the orbit the bone rises above the nerve close to the orbital 

 edge and forms a bony bridge over it. There is always a continuous 

 layer of membrane over the nerve, thicker at the margin even before 

 ossification is detectible, traceable outward to the place where the 

 malar is ossifying and onwards to the lachrymal region, and into 

 this the bony growth extends. The overlap is from without inwards, 

 and the lip of bone growing over the nerve touches the continuous 

 plate internally forming the sutura infraorbitalis verticalis on the face. 

 This has formed and the infra-orbital foramen is quite bridged in at 

 the end of the thirteenth week. About the sixteenth week the 

 margin of the outer lip of the infra-orbital canal extends over the 

 nerve behind the brim of the orbit, and thus coalescing with the 

 inner margin from before backwards forms the sutura infraorbitalis 

 longitudinalis. The point where these two sutures unite varies in 

 place arid may be at, under, or internal to the anterior point of the 

 malar bone, and, as in many cases, the part of the maxilla on which 

 the malar abuts, is prolonged inwards to support the anterior inferior 

 angle of that bone, it is not uncommon to find the front portion of 

 the sutura infraorbitalis running transversely inwards into the 

 lachrymo-maxillary suture, in this form the transversely-placed, 

 inward-running anterior limb of the suture is sometimes known as 

 the sutura infraorbitalis transversa (Halbertsma), and when this is 

 present the edge of the portion of the infra-orbital plate internal to 

 the infra-orbital nerve is thereby excluded from the brim of the 

 orbit. The oss i cu lum canalis is the terminal nodule of ossification in 

 the in-jutting extremity of the process from without. 



The early period at which these conditions appear is interesting, 

 ind the extent to which the malar encroaches on the maxilla alons? 



