35 



pell * observed in the Dugong of the Red Sea (Halicore tabernaculi, 

 R.). This condition of the heart was first noticed by Daubenton in 

 the fcetus of the Manatee ; and is also described by the unfortunate 

 Steller in the genus worthily consecrated to his name, in which, how- 

 ever, the apical cleft of the heart extended upwards only one third 

 of the way towards the base. In the Dugong it reaches half-way 

 towards the base. The carnivorous Cetacea do not participate with 

 the herbivorous section in this interesting structure. 



" I found in each of the specimens that the foramen ovale was com- 

 pletely closed, and the ductus arteriosus reduced to a thick ligament- 

 ous chord, permeable for a short distance by an eye-probe from the 

 aorta, where a crescentic slit still represented the original communi- 

 cation. In the smoothness and evenness of their exterior, and their 

 general form, the auricles of the Dugong resemble those of the Turtle 

 (Chelone) : the appendix can hardly be said to exist in either. The right 

 auricle is larger than the left ; the musculi pectinati are well deve- 

 loped, especially in the left : they are irregularly branched, and with 

 many of the small round fasciculi attached only by their two extre- 

 mities to the auricular parietes. The free wall of the right ventricle 

 scarcely exceeds at any part a line in thickness, and is in many places 

 even less. The tricuspid valve is attached to three fleshy columns 

 by chorda: tendinete given off from the sides and not the extremities 

 of the cohmneE, both of which extremities are implanted in the walls 

 of the ventricles. There are several other columnm carnece passing 

 freelv from one part of the ventricle to another, like the musculi pec- 

 tinati of the auricles, and which have no connection with the tricus- 

 pid valve. The mitral valve is adjusted to its ofhce by attachments 

 to two short and transversely-extended columnce. The thickness of 

 the parietes of the left ventricle varies from half an inch to an inch. 

 The valves at the origins of the great arteries present the usual struc- 

 ture. The primary branches from the arch of the aorta corresponded 

 in each specimen with the description and figure by Home. There 

 is one superior cava only, not two as in the elephant. The pulmo- 

 nary veins terminate in the left auricle by a common trunk an inch 

 in length. 



" With respect to the vascular system of the Cetacea, Hunter f, 

 speaking of the true whales, observes, " Animals of this tribe have 

 a greater proportion of blood than any other known, and there are 

 many arteries apparently intended as reservoirs for arterial blood ;" 

 and then he proceeds to describe the extraordinary intercostal and 

 intravertebral plexuses in the true Cetacea. As no mention is made 

 in the anatomical descriptions of the herbivorous Cetacea, by Dau- 

 benton, Steller, Cuvier, Raflfles, and Home, respecting the existence 

 or otherwise of similar plexuses in the several specimens examined 

 by them, I pursued with much interest this part of the dissection of 

 our Dugongs ; but could detect no trace of this very striking modi- 



• Beschreihung des im Rothen Meere vorkommenden Dugong. 4to. Frank- 

 furt, 1833, p. 106. 



t Philos. Trans. 1787, p. 415. 



