334 



AXA TOMICAL TECH]\^OL OGT. 



place of origin of the A. hrachio-cephalica ; (D) the right and left cardiac arteries imbedded 

 in the fat at the line of junction of the auricles and ventricles ; (E) the part marked septum 

 auricularum is not truly part of the septum, but the thick tissue ventrad of it as seen in 

 Fig. 96. 



§ 892. Fig. 94 — Preparation. — This represents nearly the dextro- ventral fourth of 

 the heart, but the two planes of longitudinal section are not quite at right angles with 

 each other, and the preparation is so placed that both are foreshortened. 



The special object is to show the dextral wall of the central part of the aorta, %vith the 

 dextral sinus Valsalvce and the mouth of the corresponding A. cardinca. This latter is 

 seen to be so high up that it would not be covered by the V. semilunaris even when fully 

 extended (§ 856). 



At the left are seen the cavity of the conus arteriosus, with a very small piece of the 

 A. pulmonalis, and one of the semilunar valves, which is decidedly upon a higher (more 

 cephalic) level than those of the aorta (§ 866). 



It will be understood that the communication between the right ventricle and the conua 

 is behind the septum ventriculare. 



Fig. 95. — Transection of the Auricles, Caudal Aspect ; x 1.5. 



§ 893. Fig. 95-98 — General Description and Mode of Preparation.— These four 

 figures represent transections of the same heart through the auricles (Fig. 95, 96) and 

 through the ventricles (Fig. 97, 98), and as viewed from the caiidal (Fig. 95, 97) or the 

 cephalic (Fig. 96, 98) aspect. The heart had been distended and hardened with alcohol 

 (§ 842), and was then transected with the large scalpel at two levels. 



In comparing the figures as representing continuous parts of the same organ, Fig. 97 is 

 to be imagined inverted upon Fig. 98, the inversion being from left to right ; then Fig. 96 is 

 to be placed upon Fig. 97 without inversion, and Fig. 95, inverted as before, upon Fig. 96. 

 The entire heart will then, in the mind, be as if viewed from the base with the ventral 

 aspect toward the observer, so that the right and left sides are inverted as compared with his. 



§ 894. Fig. 95 — The Interior of the Auricles from the Caudal Aspect.— The figure 

 illustrates the extent of the septum avriculair, and the fact that the auricular sinuses 

 appear upon the dorsal aspect, while on the ventral there are to be seen only the appen- 



