MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 205 



little planes, the one anterior and inferior, and the other superior. The angle at which these unite forum a prominent 

 ridge directed transversely in the sense of the greatest dimension of the bone; the posterior lace is profoundly exca 

 vated. At each extremity it is articulated with the, thyroid coruua. These are two straight bon\ pieces directed 

 from before back wards a in I latterly flattened; their posterior extremities give attachment to the thyrohyoid ligament. 

 These pieces unite, forming an arc. to the circumference, of which the larynx is suspended, followed by the trachea 

 and lungs. 



Each hyoid chain is composed of throe pieces, as in the preceding animals (dog and sheep) ; the lirst or superior 

 piece has the form of a very elongated cone with its base above and its summit below, its greatest dimension being 

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

 prolongation takes place at different periods, sometimes at thirty years, sometimes at sixty years. This union is to 

 be : Iways recognized by its 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 tlio liga 

 ment gives it a very variable length. From its summit proceeds the st\ lohyoid ligament, which terminates in the 

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



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 elastic-it \ . 1 1 is very slender, tapering in its superior and swelling out in its inferior part, which is attached 

 to the small hyoid comu. 



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

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

 stem, 4 or 5 centimeters long, knotted and sometimes curved and twisted, ends in a point, and in certain subjects 

 descends to the angle of the jaw. 



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

 to form the styloid process, and the other part, the great distance between the preceding piece, and the third part, 

 a distance traveled by the stylohyoid ligament, which has caused the error of authropotomists and has led thcm to 

 divide the hyoidean chain into two parts the one which has been described with th 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 studying comparatively the hyoid apparatus of man and animals. They might have 

 reeogni/cd that the styloid process of man represents the stem formed in the ruminant and in the carnivore by the 

 liist 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 descends from the 

 rigid rod to suspend the hyoid in animals. 



Several authors in works on human anatomy mention the condition described by Thomas: 

 Meckel, in speaking of the temporal bone, says* 



The muscular eminences and depressions are, first, the styloid process (prormtuit ntytuideux), at the posterior 

 extremity of the under edge of the pyramid: this varies much in 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:! 



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



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

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

 Btyloid process to consist of but a single slender piece of cartilage reaching from the temporal 

 Inwards the basihyal. It is highly probable, that the failure to find 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 ossification begins and 

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

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

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

 several pieces have not only united with the skull but have, been joined to each other, it is not an 

 easy matter always to determine the, point of union. 



In a large series of skulls in the collection of the Army Medical Museum (he following is the 

 most common condition : A short distance belo\\ or quite at. the edge of the vaginal process 1 here 

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

 discoverable at this point. Sometimes this nodosity is placed as much as a half an inch below I he 



*J. K. Mi:&amp;lt; KI:I., Manual of I )e-.eriptive Anal .1 il .nglisb Translation), London, ISoS. Vol. i ( p. r,7. 



t dray s Anatomy, 1S87, p. 144. 



