18 



longitudinally a ligament of extraordinary strength and elasticity, forming upwards the Crest ; 

 it is of a yellowish white color, and divided into several portions, through which are seen the red 

 fibres of the muscles of the neck ; a separated and very distinct flattened chord of this ligament 

 is Seen extending from the extreme point of the processes of the withers to the back of the head, 

 43, inserted strongly into the occipitalbone. It may be useful to observe that it is theseligaments 

 when over distended or injured by blows near their Insertion that leads to the disease called 

 Pole Evil. These ligaments, as we have stated, being in a high degree elastic, appear to be the 

 cause of the singular appearance in the dying horseof the head being drawn backward; for the 

 weight of the head being removed, the horse at this time usually lying on bis side and all mus- 

 cular exertion ceasing, these ligaments uncontrolled powerfuUy pull the head towards the 

 withers backwards, and with such force as often to create considerable surprize. 



Of the Thorax. This cavity is posteriorly bounded by the Diaphragm, or in common lan- 

 guage the Midriffe which like a curtain obliquely separates itfrom theabdomen ; in its circum- 

 ference muscular, in its center tendinous, which this section exhibits in an interesting manner. 

 This muscie is greatly concemed in respiration and is the chief cause of the heaving and agita- 

 tions ofthe flanks in broken wind, and other complaints affecting the lungs or intestinesafford- 

 ing often a useful means of judging of danger and of the approaches of death in these animals. 

 The great trunk of the Aorta, or chief artery, is seen passing through it near its insertion into the 

 loins and below this is seen the Aesophagus or Gullet also passing through it to go to the 

 stomach. Anteriorly the cavity of the Chest is supported by the Sternum or Breast-bone, 45 ; 

 its deep or wide surface presents several irregulär round ed patches of redder and more porous 

 bone, being the places of insertion of the ribs ; the uppermost of these 46, is singularly covered 

 withsmooth cartilage, as though it wasdesigned for anioveable Joint, it may havesome reference 

 to the clavicle of animals. Near the middle ofthe lower part ofthe chest is seen theHeart, 47, 

 with its two Chambers, the great and lesserventricle, a,b, the ferner impelling the blood through 

 the body , the latter through the lungs only , at the Upper part of the heart and over these Chambers 

 is seen the white internal coats of the Auricles, c, for receiving the blood returning to the heart, 

 and large openings are seen for its ingress to the heart and passage to the ventricles. The Heart 

 ig loosely surrounded by a membranous bag, 48, called the Pericardium, formed by a dupbca- 

 tion ofthe Mediastinum, 49, 49, 49, below, the Pericardium is attached to the Sternum. 



The Ldngs, formed of two large lobes, occupy the two cavities of the chest, havingthe medi- 

 astinum and heart between them, there is also a smaller central lobe to the lungs, which posteriorly 

 •urrounds the heart, and is seen divided, 50.The three openiug« are 3 of the air-pipes or Bron- 

 chial vessels, continuations of the canal of the wind-pipe. Through an opening in the medias- 

 tinum purposely made 51 , is seen the left cavity of the chest with a portion of the extremity of 

 the left lobe of the lungs, coUapsed from the admission of air into the cavitj' ; another portion of 

 "the lobe is seen near the Upper extremity of the sternum in the anterior part of the cavity 52 : 

 the ribs are also obscurely visible through the same openings,their internal surface being covered 

 with a fine membrane called the pleura which lines the cavity ofthe chest, and is reflected over all 

 itsviscera: The oblique fibres between the ribs are the intercostal muscles. The large tube or 



cylin- 



