Thirteen identifiable deposits of brown fat occur in the deer mouse, Peromyscus maniculatus. Drawings of these deposits and their vascular supply are presented. Blood vessels were distinguished during dissection by filling the circulatory system with methyl methacrylate. The findings show clearly the potential of brown fat to transfer heat efficiently to the blood during a situation of cold exposure of the mouse, thereby providing further evidence in support of a thermogenic role for this tissue.

Tissue concentrations of acetoacetate and β-hydroxybutyrate (ketone bodies) were determined for the blood, liver, caecum, heart, and axillary brown fat, from nonhibernating and hibernating arctic ground squirrels, Spermophilus undulatus, in late spring and during winter, respectively. AcetylCoA and acetoacetylCoA concentrations were measured in the liver, heart, and brown adipose tissue.Except that the concentration of acetylCoA remained unchanged in the liver, all tissues investigated showed elevated concentrations of acetylCoA, acetoacetylCoA, and ketone bodies during the hibernating state. From the increased concentrations of acetoacetate and β-hydroxybutyrate it was deduced that active ketone body metabolism occurs in the hibernating arctic ground squirrel, and that during hibernation, ketone bodies are probably an important source of energy.

Heart rates were studied in deeply hibernating and in arousing bats (Eptesicus fuscus). Values range from an average of 12 beats/min in deep hibernation to an average of 800 beats/min during peak arousal.Body temperatures were recorded. Arousing bats develop the "usual" anteroposterior temperature gradient.The distribution of blood was determined (Sapirstein method), and capillary organ blood-flow rates were approximated in deeply hibernating, in arousing, and in postarousal bats.The study indicates that, after the initiation of arousal, there is a redistribution of blood such that capillary blood-flow rates in organs of the anterior body rise more rapidly than do those in organs of the posterior body. A higher metabolic requirement for oxygen by brown adipose tissue as compared to other tissues, and the relatively high rate of heat production by brown fat, are thought to be largely responsible for this "shunting" of blood to anterior body regions during early arousal.

Regional distribution of blood was determined using 86Rb in torpid (summer), hibernating (winter), and arousing big brown bats, Eptesicus fuscus. Heart rates, estimated from electrocardiograms, served as an index of arousal.Measured differences in circulation include higher fractions of the cardiac output being delivered to the myocardium and kidneys of bats in torpor during the summer as compared with those in hibernation during the winter. This suggests a relatively greater work load of the heart and a higher rate of kidney function in bats at low temperatures in summer.Arousal from hibernation in winter (ambient temperature (Ta) = 5 C) requires less time than does arousal from torpor (Ta = 5 C) in summer. Heart rates increase more rapidly and shifts in regional circulation occur at a faster rate during arousal from hibernation. This is related to seasonal differences in amounts of brown fat, the major source of metabolic heat for initiation of rewarming in these bats.

Integumentary arteries in garter snakes are a continuation of intercostal arteries. They give rise to a complex network of conduits resembling in pattern the outline of scutes. The arrangement of integumentary veins approximates that for arteries; venous drainage occurs ventrally via the epigastric vein, and laterally via intercostal and spinal veins. The return of blood via this latter route during basking is presumably associated with convective heat transfer to the spinal cord enhancing the potential speed of neuronal activity.