Paper - On the Development, Ossification, and Growth of the Palate Bone of Man: Difference between revisions

From Embryology
mNo edit summary
mNo edit summary
Line 9: Line 9:
:''Draft version of online paper (notice removed when completed).'' See [[Palate Development]]
:''Draft version of online paper (notice removed when completed).'' See [[Palate Development]]


{{Historical Disclaimer}}
{{Historical disclaimer}}


THROUGH the kindness of Professor Minot of Harvard, I am able to present the result of an investigation on the above subject. I have been fortunate enough to have from him a human embryo of 19 mm. in length, in which the palate bone is just commencing to ossify. I have also from Professor Minot other embryos in which ossification is further advanced, and some material supplied to me by former pupils has enabled me to complete what it is necessary to do by aid of the microscope.
THROUGH the kindness of Professor Minot of Harvard, I am able to present the result of an investigation on the above subject. I have been fortunate enough to have from him a human embryo of 19 mm. in length, in which the palate bone is just commencing to ossify. I have also from Professor Minot other embryos in which ossification is further advanced, and some material supplied to me by former pupils has enabled me to complete what it is necessary to do by aid of the microscope.


When one looks into the various accounts given by different text-books on the subject, it is, I think, evident that the matter is worthy of further consideration. It is true there is perhaps greater unanimity with regard to the ossification of this palate bone than in the case of many others, but the factstilremains that the accounts are stilsufficientlyat varianceto justify the statement that the matter is by no means setled.
When one looks into the various accounts given by different text-books on the subject, it is, I think, evident that the matter is worthy of further consideration. It is true there is perhaps greater unanimity with regard to the ossification of this palate bone than in the case of many others, but the factstilremains that the accounts are stilsufficientlyat varianceto justify the statement that the matter is by no means setled.
Line 28: Line 29:


:Sappey (fourth edition) says:"Lepalatinapourorigineun seulpoint d'osificatiomnqueoccupel'angledereuniondesesdeuxportions. Laportion horizontales'accroitplusrapideimientetl'emported'abordsur laverticale. Plus tard, cette derniere s'allonge un peu; il s'etablit alors lune et l'autre tine sorte d'egalite. Lorsque leserins maxillaire s'agrandit, on voit ha portionverticales'allongeraussietdevenirpredoininante."
:Sappey (fourth edition) says:"Lepalatinapourorigineun seulpoint d'osificatiomnqueoccupel'angledereuniondesesdeuxportions. Laportion horizontales'accroitplusrapideimientetl'emported'abordsur laverticale. Plus tard, cette derniere s'allonge un peu; il s'etablit alors lune et l'autre tine sorte d'egalite. Lorsque leserins maxillaire s'agrandit, on voit ha portionverticales'allongeraussietdevenirpredoininante."


:Testat is content with quoting the account given by Rainbaud and Renault.
:Testat is content with quoting the account given by Rainbaud and Renault.
Line 40: Line 40:


Sections of various embryos have been examined,some from my own collection, but many from that of Professor Minot of Harvard.
Sections of various embryos have been examined,some from my own collection, but many from that of Professor Minot of Harvard.
Examination of coronal sections of a 19 mm. embryo. These were examined and drawn serially, and it will be noticed that the two opposite halves of the palate P. are at this stage vertically disposed at the side of the tongue T.,some distance above what might be expected to representthepointwheretheanglewillbeformed. Between the side of the naso-pharynx and the palate, one sees, just commencing to ossify, the palate bone P.B., and it is evident that this centre, as generally described, arisesinmembrane. Immediately to its outer side can be seen a large nerve clump caused by the palatine nerves. All other sections of this embryo show the same thing, viz., that tile palate bone is ossified just internal to the palatine nerves, and therefore in its vertical plate, ossification commencing in the 19 mm embryo. There is as yet no sign of a horizontal plate.
Examination of coronal sections of a 19 mm. embryo. These were examined and drawn serially, and it will be noticed that the two opposite halves of the palate P. are at this stage vertically disposed at the side of the tongue T.,some distance above what might be expected to representthepointwheretheanglewillbeformed. Between the side of the naso-pharynx and the palate, one sees, just commencing to ossify, the palate bone P.B., and it is evident that this centre, as generally described, arisesinmembrane. Immediately to its outer side can be seen a large nerve clump caused by the palatine nerves. All other sections of this embryo show the same thing, viz., that tile palate bone is ossified just internal to the palatine nerves, and therefore in its vertical plate, ossification commencing in the 19 mm embryo. There is as yet no sign of a horizontal plate.
   
   
Line 50: Line 51:




In an embryo of 24 mnm. in length, also supplied by Professor Minot, one sees thetwo halvesof tilepalatenow horizontallydisposed,whereasitwill have been noticed that they lie vertically disposed by the side of the tongue in the embryo of 19 nun.
In an embryo of 24 mm. in length, also supplied by Professor Minot, one sees thetwo halvesof tilepalatenow horizontallydisposed,whereasitwill have been noticed that they lie vertically disposed by the side of the tongue in the embryo of 19 mm.
Development,Ossification,andGrowthofthePalateBoneofMan 403
 
Itisatthisstagethatthehorizontalplateofthepalatebonecommences toform,but itdoes not comeofsharply-almostatrightangles-asyet; itcurves inwards quite at the lower end of the vertical plate, see fig. 2 (Harvard,24,x.378). P.B.isthepalatebone,P.thepalate,P.N.palatine nerves.
 
At a later stage, however, the direction is much more at right angles totheverticalplate. Atnotimecananyextracentreofossificationbe seen. Itistruethatbymaking,say,oneortwosectionseitherinthe horizontal or the vertical direction, one may see what appear to be two
It is at this stage that the horizontal plate of the palate bone commences to form, but it does not come of sharply-almost at right angles - as yet; it curves inwards quite at the lower end of the vertical plate, see fig. 2 (Harvard,24,x.378). P.B.isthepalatebone,P.thepalate,P.N.palatine nerves.
At a later stage, however, the direction is much more at right angles totheverticalplate. Atnotimecananyextracentreofossificationbe seen. Itistruethatbymaking,say,oneortwosectionseitherinthe horizontal or the vertical direction, one may see what appear to be two centres; but that appearanceisdue,inoneregionatalevents,toperforation of the bone by an artery from the posterior palatine to the inferior meatus andturbinatedbone. Thisforamenseemstobeconstant,andinearly fetal life is of great size (figs. 3 and 4).
 
 
FIG. 3.
FIG. 3.
P.RB.,palate bone; G.,groove for internal pterygoid plate; H.P., hamullarprocess; P.N., palatine nerves; P.P.A., post- palatine artery. The bone seems here to consist of two separate parts due to foranien.
P.RB.,palate bone; G.,groove for internal pterygoid plate; H.P., hamullarprocess; P.N., palatine nerves; P.P.A., post- palatine artery. The bone seems here to consist of two separate parts due to foranien.
FIG. 3A&.
FIG. 3A&.
H.P.P.,horizontalplateofpalatebone; T.,tuber- osity; H.P., hamular process (cartilaginous); T.P., tensor lIalati; E.T., Eulstachianl tulbe; U.P., coronoid process- N., neck of jaw; MI., malar bone;*5.M., superior maxilla, E., vertical plate of ethmoid; J.C., Jacob- son'scartilage. Owncollection,M2. Hori- zontal42mm. embryo.
H.P.P.,horizontalplateofpalatebone; T.,tuber- osity; H.P., hamular process (cartilaginous); T.P., tensor lIalati; E.T., Eulstachianl tulbe; U.P., coronoid process- N., neck of jaw; MI., malar bone;*5.M., superior maxilla, E., vertical plate of ethmoid; J.C., Jacob- son'scartilage. Owncollection,M2. Hori- zontal42mm. embryo.
centres; butthatappearanceisdue,inoneregionatalevents,toperforation of the bone by an artery from the posterior palatine to the inferior meatus andturbinatedbone. Thisforamenseemstobeconstant,andinearly fetal life is of great size (figs. 3 and 4).
 
 
It may be taken as conclusive that there is only one centre for the general mass of the bone. But what about the orbital and sphenoidal processes? are they ossified separately or by extension from the general mass?
It may be taken as conclusive that there is only one centre for the general mass of the bone. But what about the orbital and sphenoidal processes? are they ossified separately or by extension from the general mass?
Fig. 5 is a representation of a section cut sagittally, which I was lucky to get,and itshows at a very early period al thheessential parts of the palatebone. Theembryofromwhichthisseriesofsectionswascutwas
Fig. 5 is a representation of a section cut sagittally, which I was lucky to get,and itshows at a very early period al thheessential parts of the palatebone. The embryo from which this series of sections was cut was about 40 mm. in length, but was unfortunately not in the best of pre- servation and only the bone stained really well, neither nerves nor teeth beingstainedtoanyextent. Initonecanseethepalatineshelf,the maxillary process, and then, quite on the top of the vertical plate, forward and backward projections which indicate the positions of the future orbital andsphenoidalprocesses. Naturally no spheno-palatinenotchisdeveloped, but there is a slight depression on the upper border of the vertical plate whichmay betakenasrepresentingit(figs.5and6.)
404 Professor Edward Fawcett
 
about 40 mm. in length, but was unfortunately not in the best of pre- servation and only the bone stained really well, neither nerves nor teeth beingstainedtoanyextent. Initonecanseethepalatineshelf,the maxillary process, and then, quite on the top of the vertical plate, forward and backward projections which indicate the positions of the future orbital andsphenoidalprocesses. Naturallynospheno-palatinenotchisdeveloped, but there is a slight depression on the upper border of the vertical plate whichmay betakenasrepresentingit(figs.5and6.)
 
In course of time both the sphenoidal and orbital processes develop as outgrowths from the vertical plate, not by separate ossification, and it is to
In course of time both the sphenoidal and orbital processes develop as outgrowths from the vertical plate, not by separate ossification, and it is to be remarked that at quite an early stage and until birth even the sphenoi- dal process is much larger than the orbital one; in fact the orbital process appears not unlike a slender coracoid process of the scapula at this time (fig. 7, a and b), directed upwards and forwards at first and being largely maxillary in surface; then it turns suddenly upwards and backwards, being mainlyorbital. This disparity in size of the two processes is interesting as leading us back to what holds good with the quadruped palate bone. In a specimen three years old the two processes are about equal in bulk, whilst at the sixth the orbital has quite taken the lead.
>Pw_A ,
 
 
 
FIG. 4.
FIG. 4.
P.B, palate bone; G.P.N., great palatine nerve; P.P.A., post- palatineartery. Owncollection. Horizontal, above last, 42 mm. embryo.
P.B, palate bone; G.P.N., great palatine nerve; P.P.A., post- palatineartery. Owncollection. Horizontal, above last, 42 mm. embryo.
FIG. 5.
FIG. 5.
be remarked that at quite an early stage and until birth even the sphenoi- dal process is much larger than the orbital one; in fact the orbital process appears not unlike a slender coracoid process of the scapula at this time (fig. 7, a and b), directed upwards and forwards at first and being largely maxillary in surface; then it turns suddenly upwards and backwards, being mainlyorbital. Thisdisparityinsizeofthetwoprocessesisinterestingas leadingusbacktowhatholdsgoodwiththequadrupedpalatebone. Ina specimen three years old the two processes are about equal in bulk, whilst at the sixth the orbital has quite taken the lead.
O.,orbitalprocess; S.,sphenoidalpro- cess,T.,ttberosityofpalatebone; H.P.,hanmularprocess; P.M.,lire- maxilla; S.M., superior maxilla; N.C.,nasalcavity. Owncollection. Sagittal, 40 mm., No. 207.
 
 
 
 
There is another feature of interest at quite an early stage and con- tinued into childhood, that is,the enormous relative size of the groove for theinternalpterygoidplate. Inalmy specimensfrom the42mm. embryo onwards. this groove is relatively enormous in size (fig. 3, G).
There is another feature of interest at quite an early stage and con- tinued into childhood, that is,the enormous relative size of the groove for theinternalpterygoidplate. Inalmy specimensfrom the42mm. embryo onwards. this groove is relatively enormous in size (fig. 3, G).
O.,orbitalprocess; S.,sphenoidalpro- cess,T.,ttberosityofpalatebone; H.P.,hanmularprocess; P.M.,lire- maxilla; S.M., superior maxilla; N.C.,nasalcavity. Owncollection. Sagittal, 40 mm., No. 207.
 
10
 
Development,Ossification,andGrowthofthePalateBoneofMan 405
It is a well-known fact that in the fetal life the antero-posterior extent of the vertical plate is greater than the vertical (fig. 5).  
It is a well-known fact that in the fetal life the antero-posterior extent of the vertical plate is greater than the vertical (fig. 5).
 
These are the leading features of the ossification and growth of the palateboneputsomewhatdiscursively. Iwillnowputthem alitlemore concisely.
These are the leading features of the ossification and growth of the palateboneputsomewhatdiscursively. I will now put them a little more concisely.
1. The palate bone is developed by membranous ossification taking place at the side of the nasal cavity and immediately internal to the palatinenerves. Thereisnopterygo-quadratecartilageinman,soitcannot ossifyinthat.
 
2. Ossification commences in the vertical plate in embryos of some 19 mm. in length.
# The palate bone is developed by membranous ossification taking place at the side of the nasal cavity and immediately internal to the palatinenerves. There is no pterygo-quadrate cartilage in man, so it cannot ossify in that.
# Ossification commences in the vertical plate in embryos of some 19 mm. in length.
# The palatine process appears in the 24 mm. embryo, at which time the two halves of the palate have become horizontal.
# The orbital and sphenoidal processes are outgrowths from the vertical plate,andappearmuchlater. Sincetheabovewaswritten,Ihavehad evidence that the whole of the orbital process may not be formed by upwardextensionfromtheverticalplate. Asinonespecimenofthe 2nd-3rdyear,theorbitalprocessoftherightpalatebonehasafissurerunning rightthroughitatthejunctionofthelower-withtheupper2. This fissure separated off a small mass which synostosed behind with the body of the sphenoid and the sphenoidal turburated bone and in front with the ethmoid. On the opposite side the corresponding mass was fused with the ethmoid, the orbital process of the palate bone was small, whereas the lateral mass of the ethmoid was much longer on that side than the other. If we regard this mass as the epiphysis which Rainbaud and Renault have described, then it raises the interesting question as to what is its morplho- logical position. That point, I think, may well be deferred for a later paper ointhe(qIlestion. Seefig.8.
# The sphenoidal process is throughout fiftal life larger than the orbit alone.
# Up to,say,aboutthesecondorthirdyear,theantero-posteriorlength is greater than the vertical height of the palate bone.
# The groove for articulation with the internal pterygoid plate is enormously larger than the other grooves on the tuberosity.
# Chronologically the palate bone appears after the upper jaw, and is therefore third in date of appearance of the skull bones.
 
sSP A
sSP A
tS'
tS'
Line 84: Line 103:
a,seven-monthpalatebone showing smallorbitalprocess; b,younger palate bone than a, and showing a foramen in the vertical plate; c, showing groove for internal pterygoid plate.
a,seven-monthpalatebone showing smallorbitalprocess; b,younger palate bone than a, and showing a foramen in the vertical plate; c, showing groove for internal pterygoid plate.
S.P., splhenoidal; O.P., orbital process of palate bone; M.G., Mterkel's ganglion; S.P.A., spheno -palatine artery; N.C., nasal cavity. Own collection,same embryo as figs. 4 and 5.
S.P., splhenoidal; O.P., orbital process of palate bone; M.G., Mterkel's ganglion; S.P.A., spheno -palatine artery; N.C., nasal cavity. Own collection,same embryo as figs. 4 and 5.
3. The palatine process appears in the 24 mm. embryo, at which time the two halves of the palate have become horizontal.
 
4. The orbital and sphenoidal processes are outgrowths from the vertical plate,andappearmuchlater. Sincetheabovewaswritten,Ihavehad evidence that the whole of the orbital process may not be formed by upwardextensionfromtheverticalplate. Asinonespecimenofthe 2nd-3rdyear,theorbitalprocessoftherightpalatebonehasafissurerunning rightthroughitatthejunctionofthelower-withtheupper2. This fissure separated off a small mass which synostosed behind with the body of the sphenoid and the sphenoidal turburated bone and in front with the ethmoid. On the opposite side the corresponding mass was fused with the ethmoid, the orbital process of the palate bone was small, whereas the lateral mass of the ethmoid was much longer on that side than the other.
 
C.
406 Development,Ossiflcation,andGrowthofthePalateBoneofMan
If we regard this mass as the epiphysis which Rainbaud and Renault have described, then it raises the interesting question as to what is its morplho- logicalposition. Thatpoint,Ithink,maywellbedeferredforalaterpaper ointhe(qIlestion. Seefig.8.
FIG. 8.-Three-year old palate l)one, showing a separateinass(?)overorbitalprocess0.
FIG. 8.-Three-year old palate l)one, showing a separateinass(?)overorbitalprocess0.
5. The sphenoidal process is throughout fiftal life larger than the orbitalone.
 
6.Up to,say,aboutthesecondorthirdyear,theantero-posteriorlength is greater than the vertical height of the palate bone.
 
7. The groove for articulation with the internal pterygoid plate is enormously larger than the other grooves on the tuberosity.
{{Historical disclaimer}}
8. Chronologically the palate bone appears after the upper jaw, and is therefore third in date of appearance of the skull bones.

Revision as of 20:31, 13 May 2013

Read before the Anatomical Society, January 19, 1906.

<pubmed>17232695</pubmed>| PMC1287457

By Edward Fawcett, M.B. Edin., Professor of Anatomy, University College,Bristol.


Draft version of online paper (notice removed when completed). See Palate Development

Template:Historical disclaimer

THROUGH the kindness of Professor Minot of Harvard, I am able to present the result of an investigation on the above subject. I have been fortunate enough to have from him a human embryo of 19 mm. in length, in which the palate bone is just commencing to ossify. I have also from Professor Minot other embryos in which ossification is further advanced, and some material supplied to me by former pupils has enabled me to complete what it is necessary to do by aid of the microscope.


When one looks into the various accounts given by different text-books on the subject, it is, I think, evident that the matter is worthy of further consideration. It is true there is perhaps greater unanimity with regard to the ossification of this palate bone than in the case of many others, but the factstilremains that the accounts are stilsufficientlyat varianceto justify the statement that the matter is by no means setled. Where the various statements are taken from I cannot say, as no references are given, save in the case of Rambaud and Renault.

Cruveithier,p.72,English edition, 1841, says the bone isdeveloped from a single centre of ossification, which appears from the fortieth to the fiftieth day at the point of union of the vertical and horizontal portions and the pyramidal process. During its development the bone appears as it were crushed down, so that the vertical portion is shorter than the horizontal, and there is a marked predominance in the antero-posterior diameter.
Gray, sixteenth edition, says the bone is developed from a single centre which appears about the second month at the angle of junction of the two plates of the bone. From this point ossification spreads inwards to the horizontal plate, downwards into the tuberosity, and upwards into the vertical plate.

Some authorities describe the bone as ossifying from four centres: one for the tuberosity and portion of the vertical plate behind the posterior palative groove: a second for the rest of the vertical and horizontal plates; a third for the orbital, and a fourth for the sphenoidal process (this is evidently from Ramnbaud and Renault). Intilefi(Ptusthehorizontalplate is muclh longer than the vertical; and even after it is fully osified, the whole bone is at first remarkable for its shortness.

Gregenbaur (French translation by Charles Julin, 1889), says: JDe mneme que le maxillaire superieur, le palatin apparait apres la huitie'me seniaine; toutefois ses rapports de situation sont unI peu dif'rents.


Thomson (Cunninghams Text-Book of Anatomy) states that " the palate bones are developed from the ossification of the membrane covering the sides oftheoralcavity. AccordingtoRainbaudandRenault,twoprimitivecentres appearaboutthesixthweekoffetallife. Fromoneofthesethetuber- osity and the part of the vertical plate behind the posterior palative groove is developed; from the other the remainder of the bone is formed, with the exception of the orbital and sphenoidal processes, which are developed from secondary centres that make their appearance somewhat later. Other authorities describe the bone as ossifying from a single centre which appears about the end of the second month in the angle between the vertical and horizontalplates. Atbirththebomieismuch longerinitsantero-posterior diameterthan initsverticalheight,theconverseofitstypicaladultfori."
Sappey (fourth edition) says:"Lepalatinapourorigineun seulpoint d'osificatiomnqueoccupel'angledereuniondesesdeuxportions. Laportion horizontales'accroitplusrapideimientetl'emported'abordsur laverticale. Plus tard, cette derniere s'allonge un peu; il s'etablit alors lune et l'autre tine sorte d'egalite. Lorsque leserins maxillaire s'agrandit, on voit ha portionverticales'allongeraussietdevenirpredoininante."
Testat is content with quoting the account given by Rainbaud and Renault.
Quain (tenth edition) says the palate bone is ossified from a single centre, which appears in the seventh or eighth week at the angle between its horizontal and vertical parts.

2lf;catistei (p. 239) says the palatine bone is formed in a part of the pterygo-quadratecartilage,andisveryirregularandvariable. Itossifies by a single centre which appears at the front of the pyramidal process inl theseventhweek. Hqtmnphryisveryaccurate,asarule,when describingtheossificationof abone. Withreferencetothepalatebonehesays(p.296): 'Eachpalate bome is developed from one nucleus which appears between the fortieth day and the third month, at the angle of union of the horizontal with the verticalportion. The palatine process soon shoots inward to meet that of theoppositeside. In the young child the bone has very little depth;the transverse measurement is greater than the vertical, and the orbital portion is not yet formed."


Personal Observations

Sections of various embryos have been examined,some from my own collection, but many from that of Professor Minot of Harvard.

Examination of coronal sections of a 19 mm. embryo. These were examined and drawn serially, and it will be noticed that the two opposite halves of the palate P. are at this stage vertically disposed at the side of the tongue T.,some distance above what might be expected to representthepointwheretheanglewillbeformed. Between the side of the naso-pharynx and the palate, one sees, just commencing to ossify, the palate bone P.B., and it is evident that this centre, as generally described, arisesinmembrane. Immediately to its outer side can be seen a large nerve clump caused by the palatine nerves. All other sections of this embryo show the same thing, viz., that tile palate bone is ossified just internal to the palatine nerves, and therefore in its vertical plate, ossification commencing in the 19 mm embryo. There is as yet no sign of a horizontal plate.


FIG. 1. FIG.2. P.B.,palatebone;P.N.,palatinenerves;P.,palate P.B.,palatebone,justdevelopingpalatinepro- langingdownbysideoftongue,T. Harvard collection,No.819,sect.284. Coronal19mm. embryo. cess;P.,palate,nowseparatingtonguefrom baseofskulil;P.N.,palatinenerves.Harvard collection,No.24,sect.378. Coronal24mm. embryo.


In an embryo of 24 mm. in length, also supplied by Professor Minot, one sees thetwo halvesof tilepalatenow horizontallydisposed,whereasitwill have been noticed that they lie vertically disposed by the side of the tongue in the embryo of 19 mm.


It is at this stage that the horizontal plate of the palate bone commences to form, but it does not come of sharply-almost at right angles - as yet; it curves inwards quite at the lower end of the vertical plate, see fig. 2 (Harvard,24,x.378). P.B.isthepalatebone,P.thepalate,P.N.palatine nerves. At a later stage, however, the direction is much more at right angles totheverticalplate. Atnotimecananyextracentreofossificationbe seen. Itistruethatbymaking,say,oneortwosectionseitherinthe horizontal or the vertical direction, one may see what appear to be two centres; but that appearanceisdue,inoneregionatalevents,toperforation of the bone by an artery from the posterior palatine to the inferior meatus andturbinatedbone. Thisforamenseemstobeconstant,andinearly fetal life is of great size (figs. 3 and 4).


FIG. 3. P.RB.,palate bone; G.,groove for internal pterygoid plate; H.P., hamullarprocess; P.N., palatine nerves; P.P.A., post- palatine artery. The bone seems here to consist of two separate parts due to foranien. FIG. 3A&. H.P.P.,horizontalplateofpalatebone; T.,tuber- osity; H.P., hamular process (cartilaginous); T.P., tensor lIalati; E.T., Eulstachianl tulbe; U.P., coronoid process- N., neck of jaw; MI., malar bone;*5.M., superior maxilla, E., vertical plate of ethmoid; J.C., Jacob- son'scartilage. Owncollection,M2. Hori- zontal42mm. embryo.


It may be taken as conclusive that there is only one centre for the general mass of the bone. But what about the orbital and sphenoidal processes? are they ossified separately or by extension from the general mass? Fig. 5 is a representation of a section cut sagittally, which I was lucky to get,and itshows at a very early period al thheessential parts of the palatebone. The embryo from which this series of sections was cut was about 40 mm. in length, but was unfortunately not in the best of pre- servation and only the bone stained really well, neither nerves nor teeth beingstainedtoanyextent. Initonecanseethepalatineshelf,the maxillary process, and then, quite on the top of the vertical plate, forward and backward projections which indicate the positions of the future orbital andsphenoidalprocesses. Naturally no spheno-palatinenotchisdeveloped, but there is a slight depression on the upper border of the vertical plate whichmay betakenasrepresentingit(figs.5and6.)


In course of time both the sphenoidal and orbital processes develop as outgrowths from the vertical plate, not by separate ossification, and it is to be remarked that at quite an early stage and until birth even the sphenoi- dal process is much larger than the orbital one; in fact the orbital process appears not unlike a slender coracoid process of the scapula at this time (fig. 7, a and b), directed upwards and forwards at first and being largely maxillary in surface; then it turns suddenly upwards and backwards, being mainlyorbital. This disparity in size of the two processes is interesting as leading us back to what holds good with the quadruped palate bone. In a specimen three years old the two processes are about equal in bulk, whilst at the sixth the orbital has quite taken the lead.


FIG. 4. P.B, palate bone; G.P.N., great palatine nerve; P.P.A., post- palatineartery. Owncollection. Horizontal, above last, 42 mm. embryo. FIG. 5. O.,orbitalprocess; S.,sphenoidalpro- cess,T.,ttberosityofpalatebone; H.P.,hanmularprocess; P.M.,lire- maxilla; S.M., superior maxilla; N.C.,nasalcavity. Owncollection. Sagittal, 40 mm., No. 207.



There is another feature of interest at quite an early stage and con- tinued into childhood, that is,the enormous relative size of the groove for theinternalpterygoidplate. Inalmy specimensfrom the42mm. embryo onwards. this groove is relatively enormous in size (fig. 3, G).


It is a well-known fact that in the fetal life the antero-posterior extent of the vertical plate is greater than the vertical (fig. 5).

These are the leading features of the ossification and growth of the palateboneputsomewhatdiscursively. I will now put them a little more concisely.

  1. The palate bone is developed by membranous ossification taking place at the side of the nasal cavity and immediately internal to the palatinenerves. There is no pterygo-quadrate cartilage in man, so it cannot ossify in that.
  2. Ossification commences in the vertical plate in embryos of some 19 mm. in length.
  3. The palatine process appears in the 24 mm. embryo, at which time the two halves of the palate have become horizontal.
  4. The orbital and sphenoidal processes are outgrowths from the vertical plate,andappearmuchlater. Sincetheabovewaswritten,Ihavehad evidence that the whole of the orbital process may not be formed by upwardextensionfromtheverticalplate. Asinonespecimenofthe 2nd-3rdyear,theorbitalprocessoftherightpalatebonehasafissurerunning rightthroughitatthejunctionofthelower-withtheupper2. This fissure separated off a small mass which synostosed behind with the body of the sphenoid and the sphenoidal turburated bone and in front with the ethmoid. On the opposite side the corresponding mass was fused with the ethmoid, the orbital process of the palate bone was small, whereas the lateral mass of the ethmoid was much longer on that side than the other. If we regard this mass as the epiphysis which Rainbaud and Renault have described, then it raises the interesting question as to what is its morplho- logical position. That point, I think, may well be deferred for a later paper ointhe(qIlestion. Seefig.8.
  5. The sphenoidal process is throughout fiftal life larger than the orbit alone.
  6. Up to,say,aboutthesecondorthirdyear,theantero-posteriorlength is greater than the vertical height of the palate bone.
  7. The groove for articulation with the internal pterygoid plate is enormously larger than the other grooves on the tuberosity.
  8. Chronologically the palate bone appears after the upper jaw, and is therefore third in date of appearance of the skull bones.

sSP A tS' FIG. 6. A FIG. 7. a,seven-monthpalatebone showing smallorbitalprocess; b,younger palate bone than a, and showing a foramen in the vertical plate; c, showing groove for internal pterygoid plate. S.P., splhenoidal; O.P., orbital process of palate bone; M.G., Mterkel's ganglion; S.P.A., spheno -palatine artery; N.C., nasal cavity. Own collection,same embryo as figs. 4 and 5.


FIG. 8.-Three-year old palate l)one, showing a separateinass(?)overorbitalprocess0.


Template:Historical disclaimer