ME.MUIUS OF THE NATIONAL ACADKMY OF iSCIENCKS. 205 



liipiv planus, the oup anterior nnd iiireriur, and tlio other Riipcrior. Th(> uun\o at which theor iiiiitc foniiHaproiiiiii(<nl 

 ritl^e (lirui'tod traiiaversely in (ho hl'1I8« of thi< ^reatcHt dimi'iiHioii o{ the bouu; thr poHtvrior faro in prufoiiiiilly cM-a- 

 vati'il. At each oxirciiiity it is nrtit'iilatcil witli tliu thyroid curuua. Them- aro two Htraight liouy pieces dirertuil 

 from liofore bai-k wards and latterly llattcncd; tlii'ir posterior oNtreinitieHKivoattachiiifiit to thothyrohyoid li)raiiiciit. 

 ThcHo pieces iiuito, foruiiug au arc, to the circuuifRreucc of which the larynx is Buxpeudcd, Tullowed by the trachea 

 and lungs. 



Each hyoid chain is componod of three pieces, as in the prueediiiK animals (dog and sheep); the first or snpcrior 

 piece has the form of a very elongated cone with ita base above and its summit below, its greatest dimensi<in being 

 three centimeters. Its base articulated with the hyoi<l prolongation gives it a varying length. Its union with this 

 prolongation takes i)lace at different periods, sometimes at thirty years, sometimes at sixty years. This union is to 

 berlways rocognizeil by it,s nodular appearance, more or less distinct. 



The second or intermediate piece has nearly the same form as the first, except that it is much more slender; its 

 length is about two centimeters; its base articulating with the summit of the first piece at the middle of the liga- 

 ment gives it a very variable length. From its summit proceeds the stylohyoid liganient, which terminates in the 

 third piece or small cornu of the hyoid and forms a very acute angle with the greater or thyroid cornii. 



This third piece has very often the form and size of a grain of barley, but sometimes it is elongated and styliform, 

 like the intermediate piece. It, joins the extremity of the body of the hyoid in such a manner as to form an articula- 

 tion common to it and the greater cornu. The stylohyoid ligament is composed of whitish glistening fibers possess- 

 ing great elasticity. It is very slender, tapering in its superior and swelling out in its inferior part, which is attached 

 to the small hyoid cornu. 



In the normal condition in man the superior piece of the hyoid chain is united by one extremity to the hyoid 

 prolongation anil by the other to the intermediate piece. One then finds the styloid process of authors. This osseous 

 stem, 1 or 5 centimeters long, knotted and sometimes curved and twisted, ends iu a point, and in certain subjects 

 dcsiends to the angle of the jaw. 



It is this disposition, the union of the two superior pieces between themselves and with the hyoid prolongation 

 to form the styloid i)n>ce.sa, and the other part, the great distance between the preceding piece, and the third part, 

 a distance traversed by the stylohyoid ligament, which has caused the error of anthropotomists and has led them to 

 divide the hyoidean chain into two parts— the one which has been described with the hyoid, viz, the small cornu 

 or third piece, and the other which has been attributed to the temporal, viz, the styloid process. They might have 

 easily avoided this error by stiuiyiug comparatively the hyoid apparatus of man and aninjals. They might have 

 recognized that the styloid jiroccss of man represents the stem formed in the ruminant and in the carnivore by the 

 first two pieces of the chain, and that in man the articulation at a long distance of the sUmmit of the styloid process 

 with the lesser cornu corresponds to the disposition of the third much more movable piece, which <iesconds from the 

 rigid rod to suspend the hyoid iu animals. 



Several authors in works ou liuiuaii anatomy mention the cunilition described by Thomas: 

 Meckel, in speakinj^ of the temporal bone, says* 



The muscular eminences and depressions are, first, the styloid process (provcaituii slijloideua), at the posterior 

 extremity of the under edge of the pyrami<l; this varies much iu length and sometimes exceeds two. This process 

 is sometimes entirely free and is often composed of several pieces — a curious analogy with animals. 



In Gray's Anatomy it is stated :t 



The styloid process varies in size and shape and sometimes consists of several pieces united by cartilage. 



The writer's experience upon this subject is coufiued principally to observations upon the 

 adult skull. He has, however, examined a number of foetuses, in which he has always found the 

 styloid process to consist of but a single slender piece of cartilage reaching from tlie temporal 

 towards the basihyal. It is highly probable that the fitilure to tind the several elements described 

 was due to the age of the specimens examined, all of which were at or before full term. 



The most favorable age to select is somewhere between the time when ossilication begins and 

 twenty-live or thirty years. Unfortunately, in the average museum specimen of this age tlie 

 styloid process has not been i)reserved, and all that one can discover is a short peg of bone wedged 

 in between the two lainime of the vaginal process. In skulls of more advanced age, wherein the 

 several i»ieces have not only united with the skull but have been joined to each other, it is uot au 

 easy matter always to deteriniiie tlie i)oiiit of union. 



Iu a large series of skulls in tlie collection of the Army Medical Museum the following is the 

 most commou condition : A short distance below or quite at the edge of the vaginal process there 

 is a considerable swelling or nodosity, and if the subject be not too old the remains of a suture are 

 discoverable at this jioint. Sometimes this nodosity is placed as much as a half an inch below tlie 



* J. F. Mei KKl., Manual of Descriptive Anatomy (English Translation), London, 1838, Vol. I, p. 57. 

 t Gray's ..Vnatomy, 1887, p. 144. 



