PECULIAR TO HORSES. 107 



parts. The method is as follows : Send a steel pin through the edges 

 of the orifice, and wind horse hair around it after the fashion of 

 closing an orilice in the jugular vein ; havmg done so, keep the parts 

 coated with collodion. 



DESCRIPTION OF THE HEART OF THE HORSE. 



The heart of a horse is a powerful and wonderful piece of mech- 

 anism ; its function is of the involuntary order, so that regular con- 

 tractions and expansions, or beatings occur in the normal state, with- 

 out the animal being conscious of the same ; these contractions and 

 expansions, however, can be modified, by means of various medici- 

 nal agents which act upon the nervous sy.«tem, thus producing a sort 

 of mixed action — voluntary and involuntary — all medicines known 

 as sedatives^ operate to depress the action of the heart, and lessen 

 for a certain time the number of its pulsations ; while on the other 

 hand, stimulants augment action, and increase the number of heats. 



The weigJit of the heart is about seven pounds, yet considerable 

 variations in this weight will occur among the various breeds of 

 horses, even at an adult age. For example: A horse having a coars^ 

 and gigantic, bony, and muscular organization, will be likely to be 

 in possession of a much larger heart than a compact horse of the ner- 

 vous temperament, even although both shall be of the same age. 



The ipJerior of the heart is divided into four cavities, two of 

 which being in the superior and anterior direction, and in conse- 

 quence of bearing some resemblance to the external conformation 

 of the ears of a dog, are termed atcricles / the auricles, therefore, 

 should be known as the superior cavities of the heart. These cavi- 

 ties are known as right and left, or rather anterior and posterior ; 

 their division occurs through the intervention of their septum, or 

 wall of muscle, known as the septum auriculoriwi. 



The right auricle is the receptacle for venous blood, and three 

 venous trunks terminate in it, viz., the anterior vena cava, which 

 returns the venous blood from the anterior extremities, head and 

 neck — next, the vena cava posterior, which returns the venous blood 

 from the posterior parts, and lastly, the coronary vein ; the latter 

 returns blood w^hich has circulated through the heart itself for its 

 own nourishment. A considerable quantity of dark venous blood is 

 generally found in this auricle after death, and it opens into the right 

 or antei'ior ventricle, by an aperture denominated the auriculo-ventri- 

 cular opening, yet in consequence of a valvular contrivance within 

 the ventricle, the blood cannot recede into the auricle. 



Internally, the right auricle is lined by a glistening vascular mem- 

 brane, having on various parts of its surface, small muscular emi- 

 nences, termed musculi pecunati ; the small cavities which occur, in 

 consequence of this arrangement, are termed cul-de-sacs. The rights 

 or venous ventricle, is also lined by a nicely' organized membrane, 

 and has beneath it several muscs.;lar prominences named carnm col- 

 umnm which give origin to as many tendinous slips, which are known 

 as chordce tendinoe ; they are inserted into a fibrous membrane in the 

 region of the articulo-ventricular opening, and then get the name 



