MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 205 



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

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

 vated. At each extremity it is articulated with the thyroid coriiua. These are two straight liony pieces cl. 

 from before backwards and latterly flattened ; their posterior extremities give attachment to the tliyrohyoid ligament. 

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

 and lungs. 



Kach hyoid chain is composed of three pieces, as in the preceding animals (dog and sheep) ; the first 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 uniou with this 

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

 berlways 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 the- liga- 

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

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



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

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

 tion common to it and the greater eornu. 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 coruu. 



In the 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 the styloid process of authors. This osseous 

 stem. ! 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 hyoid prolongation 

 to form the styloid process, 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 lias 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 

 recognized that the styloid process of mini 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 coruu 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 iu 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 (proeesnus styloideus), 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 :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 confined principally to observations upon the 

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

 styloid process to consist of but a single slender piece of curtilage reaching from the temporal' 

 towards the basihyal. It is highly probable that the failure to lind 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 the following is the 

 most common 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 point. Sometimes this nodosity is placed as much as a half an inch below the 



" J. F. MECKKI,, Manna! of I)e.-,criptive Anatomy (Kuglisb Translation), London, 1S3K, Vol. I, p. 57. 

 t Gray's Anatomy, 1S87, p. 14-1. 



