. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 652 CIRCULATION. Fig. As the the Insects. any other parts (fig. 325 **, a, v). A net- work of vessels is also distributed over the surface of the imperfectly formed wings, the metamorphosis from the larval to perfect state advances, and shortly after insect leaves the water to assume the aerial condition, the circulation of the blood be- comes gradually confined to a more and more circumscribed space. The loops extend- ing into the wings, limbs, caudal processes, and antennae, become shorter; when the meta- morphos
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 652 CIRCULATION. Fig. As the the Insects. any other parts (fig. 325 **, a, v). A net- work of vessels is also distributed over the surface of the imperfectly formed wings, the metamorphosis from the larval to perfect state advances, and shortly after insect leaves the water to assume the aerial condition, the circulation of the blood be- comes gradually confined to a more and more circumscribed space. The loops extend- ing into the wings, limbs, caudal processes, and antennae, become shorter; when the meta- morphosis is complete, they become entirely closed, and in general this change is followed by the disappearance of the inferior lateral or returning currents also. These remarkable changes in the circulatory organs at once indi- cate an interesting relation of their condition to the changes in the mode of life of the insect. In the aquatic state, the caudal and lateral laminae, antenna, and wings may be considered as serving the purposes of gills, for the blood is carried to them, and exposed upon their surfaces to the action of the water. The larvee of the neuropterous insects generally feed largely, but their life during the perfect condi- tion, when the circulation has ceased, is of short duration, and they either take very little food, or live in absolute abstinence. It has been also shewn that the dorsal vessel consists of different compartments, between each of which a valvular apparatus (fig. 325*,.r) prevents the passage of the blood in a retrograde direction. There are lateral openings in the neighbourhood of the valves, by which it would appear that the blood is admitted into the dorsal vessel from cross branches (Jig. 325**, y) passing directly from the lateral streams. It may be mentioned that the larger returning streams of blood, situ- ated on the lower side of the body, are said by Carus and Wagner, we cannot judge with what reason, not to be inclosed within vascular p
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