. Elementary text-book of zoology. 346 CHORD AT A. completely mix and every organ would on contraction of the ventricle be supplied with mixed blood. On the other hand, greater efiSciency would be attained if the arterial blood could be sent to the tissues generally and venous blood to the lungs, and this is practically the case. The ventricle contracts rapidly after the auricles, before the blood from the latter has had time to mix, and hence the first portion of the blood leaving the ventricle is nearly all venous, because the opening of the truncus inclines to the right. This passes up the
. Elementary text-book of zoology. 346 CHORD AT A. completely mix and every organ would on contraction of the ventricle be supplied with mixed blood. On the other hand, greater efiSciency would be attained if the arterial blood could be sent to the tissues generally and venous blood to the lungs, and this is practically the case. The ventricle contracts rapidly after the auricles, before the blood from the latter has had time to mix, and hence the first portion of the blood leaving the ventricle is nearly all venous, because the opening of the truncus inclines to the right. This passes up the wide passage to the pulmonary arches, and only when these are comparatively full does the next portion of mixed blood diverge up the smaller aperture to the top of the truncus arteriosus. Here it passes up the wide open- ings of the two systemic arches, whilst only the last and most arterial portion reaches the small aperture to the carotids, ensuring a supply of pure blood to the brain. Fig 244-â -Dorsal View of Brain of Frog. -Olfactory Nerve. Olfactory Lobe. Pineal Stalk. 4th Ventricle.,. Medulla Oblongata. The spinal nerves are clearly seen lying in the dorsal wall of the abdominal cavity. The first spinal, called the hypo- glossal, lies ventrally to the tongue, and can be Nervous. ^^^^ ^^ removal of the mylohyoid muscle. It joins the spinal cord between the first two 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 Masterman, Arthur Thomas. Edinburgh, E. & S. Livingstone
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