. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. CIRCULATION IN THE ARACHNIDA. 229 which, as they undergo no metamorphosis, consti- tutes a permanent part of their organization. Fig. 346 shows the dorsal vessel of the Aranea domestical or house spider, with some of the arterial trunks 346 „,,,__„^ arising from it, lying imbedded in a thick mass of substance, having a similar oily character to that which is contained in large quantities in the principal cavities of insects. It is, in general, difficult to o
. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. CIRCULATION IN THE ARACHNIDA. 229 which, as they undergo no metamorphosis, consti- tutes a permanent part of their organization. Fig. 346 shows the dorsal vessel of the Aranea domestical or house spider, with some of the arterial trunks 346 „,,,__„^ arising from it, lying imbedded in a thick mass of substance, having a similar oily character to that which is contained in large quantities in the principal cavities of insects. It is, in general, difficult to obtain a view of the circulation in the living spider, on account of the thick covering of hair which is spread over the body and the limbs; but if a species, which has no hair, be selected for examination, we can see very distinctly, through the microscope, the motion of the blood in the vessels, by means of the globules it contains, both in the legs and in other parts, where it presents appearances very similar to those already described in the limbs of the larvae of insects. The simplest form of a complete vascular cir- culation is presented in the Annelida. Their vessels are so disposed that the blood, receiving the in- fluence of the air principally through the medium of the integuments, or of respiratory organs imme- diately under the surface of the body, pursues its course along the back and sides of the body with- out interruption : and consequently the distinction between arteries and veins is altogether lost among the minute branches of that network which com- poses the principal part of the vascular system. The carbonised and the oxygenised portions of the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Roget, Peter Mark, 1779-1869. London : W. Pickering
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