ANATOMY. 



consists of two Irregularly quadrangular 

 pieces, united in front at an obtuse angle. 

 This part projects in the front of the neck, 

 and much more conspicuously in the male 

 than in the female sex : it is called po- 

 nuim Adumi. 



The cricoid cartilage may be compared 

 to a ring with a seal, of which the broad 

 or seal part is placed behind, and the nar- 

 rower portion in front. It is directly un- 

 der the thyroid cartilage. 



The arytenoid are two pyramidal por- 

 tions of cartilage, connected by regular 

 moveable articulations to the back of the 

 cricoi<".. 



The epiglottis is the softest cartilage of 

 the larynx. It has a basis firmly tied to 

 the thyroid cartilage, while its opposite 

 extremity, which is very thin, is of a 

 rounded figure, and stands directly up- 

 wards, except during deglutition, when it 

 descends so as to cover the opening of the 

 larynx. 



The thyroid cartilage is tied by three 

 ligaments to the os hyoides above, and by 

 as many to the cricoid cartilage below ; 

 but the most important ligaments of these 

 parts are the iigamenta glottidis ; which 

 arise from the front of 'the arytenoid car- 

 tilages, and are attached to the posterior 

 surface of the front portion of the thyroid: 

 A longitudinal slit, called the rima glotti- 

 dis, is left between these, and it is by the 

 passage of the air through that slit that 

 the voice is formed. Hence, from the 

 great share which these ligaments have in 

 forming the voice, the name of chords 

 vocales has been given tothem. 



The larynx is lined by a vascular and 

 very sensible membrane, copiously mois- 

 tf-.i L-cl with mucus, in order to defend it 

 from the external air. It admits of free 

 motion in the neck, and its parts are also 

 moved on each other ; particularly the 

 arytenoid cartilages, whose movements, 

 by Altering the size of the ruina glottidis, . 

 and the: state of tension of the chordae vo- 

 cales, contribute most immediately to the 

 variations in the tone of the voice. 



The trachea is that portion of the aerial 

 tube, which is placed between the cricoid 

 cartilages and the origin of the bronchi. 

 It isa cylindrical membranoustube, of from 

 5 to7-8thsofan inch in diameter. It 

 runs along the middle of the fore-part of 

 the neck, having the large blood-vessels 

 of the head on each side, and being con- 

 nected behind to the oesophagus. Soon 

 after it has entered the chest, it divides 

 into the two bronchi. 



The tube of the trachea is furnished 

 with hoops of cartilage, by which it is 



kept permanently open for the passage of 

 the air; these are not, however, complete 

 circles, being deficient behind. The lin- 

 ing of the tube is highly vascular and 

 sensible, and covered with a copious mu- 

 cous secretion, which is rendered neces- 

 sary by the constant current of air to 

 which it is exposed. 



The bronchi are merely the two bran- 

 ches into which the trachea divides for 

 the two lungs ; and of these the right is 

 the largest and shortest. They ramify 

 through the lunges dividing into smaller 

 and smaller branches ; and the ultimate 

 ramifications communicate with the air- 

 cells. 



ORGANS OF CIRCrLATIOX. 



The heart is the centre of the circulat- 

 ing- system ; being the source of the ar- 

 teries, and the termination of the veins. 

 The younger the subject, the larger is 

 the heart in proportion to the body. It is 

 often smaller in tall and strong men, than 

 under different circumstances. 



It is connected at its posterior part, be- 

 hind the sternum, by the large bloodves- 

 sels, being unattached every where else, 

 and merely confined in its situation by the 

 pericardium. 



The pericardium is placed in the cavity 

 of the chest, behind the second, third, 

 fourth, and fifth ribs of the left side. It 

 is covered to the right and left by the 

 bags of the pleura, which adhere by a 

 loose cellular membrane It is not actual- 

 ly connected by any part of its surface 

 to the sternum. Below, it rests on the 

 diaphragm, and adheres very firmly to the 

 superior surface of the tendon of that 

 muscle. 



The cavity of the pericardium is 

 larger f han the heart, so that this viscus 

 can move freely in it. 



The bag of the pericardium in shape 

 resembles the figure of the heart itself, 

 being conical. Its substance is thick and 

 compact, and it is much more dense and 

 strong than the peritoneum or pleura. 

 Where the great vessels are connected 

 to the heart, this membrane becomes re- 

 flected over its surface ; and hence the 

 substance of the heart has a close invest- 

 ment from this membrane, besides being 

 contained loosely in the bag-like portion. 

 A small portion of the large blood-ves. 

 sels is included within the cavity of the 

 pericardium ; particularly of the aorta 

 and pulmonary artery; which are conse- 

 quently covered by the reflected por- 

 tions. 



The internal surface of 



