////. Ill AHT. f>03 



Tin I' it j'ni-1 , concave from before to behind, includes the arterial trunks 

 which leave tin- l>-ise of the heart. 



Kadi <>!' tin- extremities, <mt, rlor uiul j>* istitutes a detaehe<l 



portion, mimed the n/<y inli.r inirii-nlnfix ; tin sr appendages are cnrv. d 

 towards each other in being flattened from above to bulow. Tlieir convex 

 In ii der is more or less crenelated, like the margin of a cock's comb, and their 

 culminating portion advances nearly to the pulmonary artery, above the 

 trunk of the cardiac vessels (Fig. 258). 



The base of the auricular mass, opposed to the base of the ventricles, 

 jiaratcd i'roui it at its periphery by the horizontal groove of the heart. 



3. Internal Confunituliim of the Heart. 



l'i> 1*1 ration. It suffices to make a longitudinal incision before and 1 liind the organ, 

 in order to expose its cavities. (I have followed Wilson's directions for many years when 

 examining the interior of the heart, and as u careful inspection of it is often necessary in 

 t an ant-pay, 1 think the student should practise the btst method of laying 

 open tli'-s:- c;i\ ities. The right auricle is prepared l>y making a trun.-vcrse incision along 

 it.s ventricular margin, from the ap{>endix to its right border, and crossed by a perpendi- 

 cular inci.-ion, carrit d from the side of the anterior to the posterior cava. The right 

 ventricle is laid open by making an incision parallel with, and a little to the right of, the 

 middle line, from the pulmonary artery in front, to the apex of the heart, and thence by 

 the side of the middle line behind to the auriculo-ventricular opening. The interior of 

 tie- left auricle is exposed by a J_ -shaped incision, the horizontal section being made 

 :he border which is attached to the base of the ventricle. The latter is opened by 

 an incision a little to the left of the septum ventriculorum, and continuing it 

 apex of the heart to the auriculo-ventricular opening behind.) 



If the heart, when viewed externally, appears to be a single organ, it is 

 not so when examined internally. The vertical septum which divides it 

 into two bilocular pouches, in reality makes two hearts of it one for the 

 dark, the other for the red blood. We will successively study these two 

 cavites by commencing with the partition that separates them. 



A. CARDIAC SEPTUM. The superior part of this septum, placed between 

 the two auricles, is named the interauricular partition (septum auricuhinnn). 

 Tin- inferior portion constitutes the mteneitfriimlar partition (ttcptinn n n- 

 trlriili.runi). The first, thin and not extensive, is perforated in the fietus by 

 the f"i-n, uen of BotuI (/>/<//. ocalf). The second, thick in its centre, thins 

 a littk- towards its borders. 



B. DARK-BLOOD (or PULMONARY^ HEART. The two superposed cavities 

 forming this poiu-h are situated in front and to the right. They are indif- 

 ferently named the anterior or rijlit rarities of tho heart: the latter term 

 being in most general use, though tho first is much more convenient in 

 Veterinary Anatomy. 



RIGHT VENTRICLE. The right ventricle represents a hollow cone, tin 

 horizontal section of which resembles a crescent, its posterior plane IM ing 

 jtii>lu-d into tho cavity by the left ventricle. 



It offers two walls, on ap<:r, and a base. 



Wnlh. The anterior wall is concave ; its thickness is more considerable 

 above than below, and averages 6-lOths of an inch. The posterior wall is 

 convex, and formed by tho septum ventriculorum. 



Until walls are uneven, from tho presence of fleshy columns (W /;< 



.r), which wo will commence examining in a general manner, as they arc 



found in tho four compartments of the heart. They are of three kinds : 



one kind, named the y////"/> </'/// heart (columnseor miitm!! ]>njiill<trtx), thic-k 



and short, and fixed by their bane to tho walls of the ventricles, have a free 



I 



