.'.us THE CIHCl'LATaJi Y A I'l'.l /M 77X 



serous membrane covering it, and which must !>< ai once n moved. Tin- furrow* >hoidd 

 then lie 1-1. :iit. 1 of their vessels and fat; this render.-) the Miperficiul muscular liKred 

 :<l>parcnt. '1'lie same re.-ult may IM- attained liy immcr.-ing tl.e heart in vinegar or 

 dilute hydrochloric acid. To isolate the ventricles and unitive films I'mm eaeh other, 

 tlie following procedure may be adopted: After removing the auricular mass and 

 dissecting the fibrous rings, the unitive lilnv.s around the.-e are divided with the point of 

 the 6calj>el, caro being taken not to injure the proper fibres. Then, with the aid of the 

 finger-nail or handle of the scalpel, follow the more or less artificial limit of the.-e two 

 series of muscular planes in a spiral manner; the vessels pausing through tin- walls of 

 the heart must bo cut through. The same course is followed in the substance of the 

 intervcntricular septum, in order to separate the two sacs formed | P y the proper fibres. 



(It will be found that Ihe simplest and best wny to prepuro the heart for an examina- 

 tion of its fibres, is t > steep it in a very weak dilution of hydrochloric acid. Jicmove the 

 serous membrane, and the fibres can then be traced, layer by layer, from their origin to 

 their termination.) 



Tho muscular tissue composing the heart rests on a fibrous framework, 

 disposed in rings around the auricnlo-ventricular and arterial openings ; it 

 receives vessels and nerves, and while covered in the internal cavities by two 

 independent serous membranes, it is enveloped, externally, by another 

 membrane of the same kind. An annular framework, muscular tumefraper t 

 vessels and nerves, and serous tunics such are the elements entering into 

 the organisation of the heart. 



A. FIBKOUS KINGS. These are also named the fibrous zones of the heart, 

 and are four in number : one for each of the openings at the base of the 

 ventricles. 



Tho two arterial zones (the pulmonary and aortic) constitute two complete 

 rings, which arc not disposed in a circular manner around the pulmonary 

 aortic openings, but arc divided into three regular festoons with their con- 

 cavities superior and internal, and which correspond to the insertions of 

 the three sigmoid valves. These zones are continuous, by their superior and 

 external contour, with the walls of the arteries, from which they arc only dis- 

 tinguished by their whitish-grey colour and slight elasticity, the arterial 

 tissue being yellow and very elastic. Their internal and inferior outline 

 sends three thin prolongations into the serous duplicaturcs of the siginoid 

 valves. 



The auriculo-ventricular zones do not completely surround the openings 

 they circumscribe. They are flattened, brilliant-white tendons, laid one 

 against the other at the level of the ventricular septum, and against 

 the aortic ring ; they turn to the right and left around the auriculo- 

 ventricular openings, but without joining at their extremities, which are 

 dispersed as fibrilla) in the muscular tissue of the ventricles. Above, these 

 zones give attachment to the muscular fibres of the auricles ; below, to the 

 ventricular fasciculi. Their internal and inferior border is prolonged into 

 the mitral and tricuspid valves, and is continuous, through these valves, 

 with the tendinous cords fixed to the walls of the ventricles. Some of theso 

 cords, generally the strongest, arc even directly inserted into the auriculo- 

 ventricular zones. 



It must be noted that, in Solipcds, there is constantly found, at the 

 point where the aortic and auriculo-ventricular zones lie against each other, 

 a more or less developed cartilaginous body, which, in the larger Ruminants, 

 is transformed into true bone. (Lavocat speaks of two cartilaginous points, 

 one to the right, at the junction of the aortic with the left auriculo- 

 ventricular ring and the cardiac septum ; the other, less developed, on the 

 left, at the origin of the left ventricular groove.) 

 _ B. MDSCULAB TISSUE. The muscular tissue composing the mass of the 



