The systemic arterial pattern of the guinea pig was studied to determine the arrangement of the major arterial trunks and their branches. Fifty-nine specimens were examined by dissection, angiography, and corrosion casting. The arterial arrangement was found to resemble a typical mammalian pattern, although some exceptions were noted. For example, the internal carotid arteries were small and of questionable significance in the cerebral blood supply. Instead, a major portion of the blood supply to the brain appeared to be provided by the internal ophthalmic arteries. In the thoracic region, large dorsal scapular arteries originated and were distributed in part to the large fat pad in the dorsal cervical region. Also, each vertebral artery arose as two separate rami that anastomosed a few millimeters from their origin. The arterial pattern of the thoracic limb presented no unusual features.Although the guinea pig is used in many phases of biomedical research, relatively little has been reported concerning its gross morphology in general and the arterial pattern in particular. Potter et al. ('58) mapped the general arterial and venous pattern using dissection as their investigative method. Froger's study ('66) included the head, thorax, and thoracic limb. His investigative techniques included dissection, angiography, and corrosion casting. A similar study by Favre ('67) was limited to the abdomen, pelvis, and pelvic limb. Dissection studies of the abdominal aorta and its branches have been reported recently by Perneczky ('69) and in a n earlier dissertation by Luther ('23). More specific investigations include a study of the arterial supply to the mandible by Boyd et al. ('67) using dissection and corrosion casting, and a dissection study of the spinal cord supply by Knox-Macaulay et al. ('60).This study was undertaken due to the scarcity of anatomical information regarding this important research animal and the frequent disagreement of existing references. MATERIALS AND METHODSTwenty-nine males and 30 females of the species Cavia porcellus averaging 800 gm in body weight were used. Eighteen specimens were examined by gross dissection, corrosion casts were made of 13, and 28 were used in angiographic studies.All of the animals were anesthetized by intraperitoneal administration of sodium pentobarbital (Diabutal).' They were heparinized and exsanguinated and the specimens for gross dissection were embalmed with approximately 200 cm3 of 10% formalin solution. They were subsequently injected intra-arterially with red latex solution.Corrosion casts were prepared by injecting exsanguinated animals with colored vinyl acetate s~l u t i o n .~ These specimens were then placed in plastic containers, covered with concentrated HC1, and placed in a fume hood for two days. Tissue debris was washed away under running tap water leaving vinyl casts for subsequent study.Specimens for angiography were prepared by injecting exsanguinated animals with a suspension made of equal volumes of water and barium sulfate (Micropaque...

The systemic arterial pattern of the guinea pig was studied to determine the arrangement of the major arterial trunks and their branches. Fiftynine specimens were examined by dissection, angiography or corrosion casting. The arterial arrangement was found to resemble a typical mammalian pattern, although some exceptions were noted. For example, the guinea pig usually has a single vessel, the celiacomesenteric trunk, instead of separate celiac and cranial mesenteric arteries. The celiac components of this vascular axis were found to originate in four different patterns. Also, the renal arteries were found to be single or double on either side with double origins more frequent.

The gross anatomy of the portal vein of 21 dogs was studied by venous portography, corrosion casting, and gross dissection. The portal vein in all specimens originated by confluence of the cranial and caudal mesenteric veins. Its large tributaries were the splenic and gastroduodenal veins, which entered the portal vein between its origin and the hepatic porta. At the hepatic porta, the portal vein divided into a short right branch and a larger left branch. The right branch ramified in the caudate process of the caudate lobe and in the right lateral lobe of the liver. The left branch was essentially the continuation of the portal vein from which successive branches passed to each of the remaining lobes of the liver and the papillary process of the caudate lobe.

The systemic arterial pattern of 59 guinea pigs was examined by dissection, angiography, or corrosion casting. The blood supply to the pelvis and the pelvic limbs arises as two terminal branches of the aorta, the right and left common iliac arteries, and each of these divides into external and internal iliac arteries. Their pattern of distribution resembles a typical mammalian pattern. The external iliac artery passes throught the body wall to supply the pelvic limb and the internal iliac artery is distributed primarily to the pelvic region and its viscera.