400 



CEUSTACEA. 



systemic, is partly branchial, and impels the blood, not through the 

 body only, but also to the respiratory organs. This view of the subject, 

 which we are disposed to consider as the most correct, is exhibited in 

 the diagram annexed. Setting out from the heart, we find that the 

 blood goes to all parts of the body through the different arterial trunks, 

 and by the great sternal artery (fig. 201, Jc) is conveyed to the legs, 

 foot-jaws, and false feet. But from this same artery (m), vessels (o o o o) 

 are furnished to the branchiae. The branchial arteries so derived 

 (fig. 204, g) subdivide into secondary trunks (h h h), which ramify 



Transverse section of the body of a Lobster, just behind the heart: a, cut edge of the shell of 

 the back ; 6, the under surface or sternal aspect ; c, the posterior end of the heart ; d d, two orifices 

 of veins entering the heart ; e, cut end of the superior caudal artery ; /, the trunk of the large artery 

 (sternal) going to the legs and gills (fc in fig. 201) ; g, trunk of an artery going to supply one tier of 

 gills ; A h A, the branches going to each gill; t, artery of the leg; kkkk, the internal vessels or 

 veins from each gill ; I, the common trunk or branchial vein ; m w, the gills ; n n, the fiabella, or 

 laminae subservient to the movement and renewal of the respired medium ; o o, basal joints of the 

 legs. 



through the individual branchiae and supply all their appended filaments. 

 Having undergone exposure to the respired medium, the blood is again 

 collected from the branchiae by branchial veins (k Tc Jc), represented on 

 the opposite side of the body, and conveyed by the large vessel (Z) to 

 the dorsal sinus (fig. 203, 6), where, being mixed up with the general 

 mass of blood contained in the sinus, the circulating fluid is admitted 

 into the heart through the valvular orifices (fig. 204, d d), to recom- 

 mence the same track. 



(1023.) In the Crustacea, as in the class of Insects, the blood* occupies 

 * Milne-Edwards, loc. cit. 



