1. A new technique has been developed for the preparation of a permanent parotid fistula in the sheep. The advantage over the Pavlov‐Glinski operation is that the saliva drips from the dependent point of a skin teat. The secretion rate may be unobtrusively observed without fixation of any apparatus to the animal. Thirty‐seven sheep with parotid fistulæ have been studied. 2. The presence of a parotid fistula for 6–93 weeks did not involve any anatomical or histological deviation from normal in the parotid gland. 3. A sheep with a parotid fistula lost each day 1–4 l. of hypertonic alkaline saliva containing 160–650 m.equiv. of Na+. The animal could be maintained in good condition indefinitely provided enough Na+ was given to replace that lost from the fistula. Digestion proceeded normally. 4. The rate of parotid salivary secretion increased during eating and rumination, and decreased during starvation or water depletion. 5. The response of the animal to Na+ depletion was examined under strictly controlled conditions. The sheep has remarkable parotid and renal mechanisms of electrolyte regulation. The salivary Na+ concentration falls commensurately with Na+ depletion from a normal of 180 m.equiv/l. to as low as 10 m.equiv/l., and the salivary K+ concentration rises equivalently from 10 m.equiv/l. to 180 m.equiv/l. This allowed the sheep to establish a new Na+ equilibrium at a particular level of Na+ depletion. It could survive for weeks even though depleted of several hundred m.equiv. of Na+. Because of the nature of the fluid dynamics of digestion in the ruminant, the mechanism of conservation of salivary Na+ during Na+ depletion may have survival value under stringent environmental conditions such as drought. 6. A sheep with a parotid fistula licked 5–15 g./day off a salt block which was provided in its cage. Prior to operation a normal sheep usually licked off only 0·5–2 g./day.

It is well known that the continued removal of gastric juice from animals or man does not radically alter the composition of the juice (Dragstedt & Ellis, 1930; Katsch & Mellinghoff, 1933). This was found despite the loss of up to half the body chlorides (Lim & Ni, 1925-6). McCance (1938) reviewed the literature on the effect of salt deficiency on the electrolyte composition of body secretions. In his own experiments he produced depletion by a deficient diet and repeated sweats. The depletion was great enough to reduce the extracellular chlorides of his subjects by 40-50 %.He found that in mixed saliva, gastric secretion and sweat there was a fall in Na+ concentration and a rise in K+ concentration. However, the changes in the first two were small, i.e. roughly reciprocal changes in Na+ and K+ of about 5-10 m-equiv/l. In the case of sweat glands, the Na+ and C1-loss in each episode decreased with increasing depletion. Whereas initially 150-180 m-equiv Na+ were lost each time, finally (7th-8th day) only 60-80 m-equiv were lost in about the same volume. There was a small gradual rise (5-10 m-equiv) in the K+ loss.Gross Na+ depletion has been produced in dogs by pancreatic fistulae (Gamble & McIver, 1928;Hartmann & Elman, 1929;Johnston & Ball, 1930).The total base concentration of the pancreatic secretion decreased as the total base of the plasma decreased. The observations of Johnston & Ball (1930), though not conclusive on this point, indicate that there was no rise of K+ in the pancreatic juice as the animal became Na+ depleted. This paper is concerned with reporting a rather striking relation between the electrolyte balance of the sheep and the composition of parotid gland secretion.The normal sheep secretes 4-8 1. of alkaline parotid saliva each day. This buffers the products of bacterial fermentation in the rumen. The transplantation of one parotid papilla and duct on to the cheek permits the subtraction of

Adrenal glands of foetal sheep of 40 days gestation to term were incubated with and without ACTH or an increased [K+]. With ACTH, the 40 day foetal adrenal was capable of producing more cortisol and aldosterone per g body weight than was the term adrenal. ACTH was a potent stimulus to aldosterone and cortisol production in foetuses aged 60\p=n-\90days, and this effect declined significantly in the 91\p=n-\120day period. An increased [K+] was stimulatory to aldosterone production only after 120 days gestation. Peripheral blood levels of aldosterone, corticosterone, cortisol, 11-deoxycortisol and 11-deoxycorticosterone were measured in foetuses 60 days to term and the levels of aldosterone and cortisol were significantly lower in 90\p=n-\120day foetuses than in the younger or older ones. Direct adrenal vein cannulation proved all five steroids to be secretory products of the foetal adrenal.The ovine foetal cortex has been shown to play a significant role in the onset of parturition in this species (Liggins 1968) and for this reason its ability to

No abstract

Secretion by the parotid gland of the sheep has been studied in acute preparations and by means of fistulae. The sheep is unusual in having a continuous flow of parotid saliva which increases in amount both with feeding and with cud chewing (Ellenberger & Hofmeister, 1887). As in the ox its parasympathetic nerve supply arrives via the buccal branch of the mandibular nerve as fine branches which go from the anterior border of the masseter muscle with the duct to the gland (Moussu, 1888(Moussu, , 1890, not via the auriculo-temporal nerve. Moussu demonstrated that after section of this nerve the gland continued to secrete and he attributed this continued secretion to a non-nervous mechanism postulated by Colin (1886). Eckhard (1893) who in 1867 (Eckhard, 1867), before Moussu's discovery, had convinced himself that there was no secretomotor nerve to the gland, held the view that it was due to the 'nature' of the gland.Eckhard (1893), after amplifying these observations and confirming Moussu's observation that stimulating the buccal branch of the mandibular nerve (henceforth referred to as Moussu's nerve) increased secretion, nevertheless stated that section of the nerve did not cause any reduction in the rapidity of secretion by the gland. This view has not been refuted, and is often quoted with the reservation that it requires confirmation (Langley, 1898, in Schafer's Physiology text-book; Babkin, 1944). It is associated with statements that salivary secretion in the ruminant is not stopped by atropine. However, the reduction by atropine of normal secretion to a lower rate is recognized by Babichev, Perstnov & Kulesco (1930) as indicating a biphasic secretomotor mechanism. In this paper we have endeavoured to establish with certainty the effect of the parasympathetic nerve on the gland.Another controversial matter is the effect of stimulation of the sympathetic fibre', to the parotid upon its secretory activity. Eckhard (1869) attacked the

The effect of water deprivation for 1 day on Na balance was measured in rats, rabbits, and sheep. In all three species, dehydration induced a considerable increase in the daily output of Na in urine. This resulted in the water-deprived animals becoming Na depleted as well as water deficient. Experiments were also designed to control for the reduced food intake that results from water deprivation in rats and rabbits. The results showed that decreased food intake was not the cause of the natriuresis and subsequent Na depletion that occurred during dehydration. When water was again made available to the dehydrated animals, a period of urinary Na retention ensued. This Na retention usually continued until the Na deficit that had accrued during the period of dehydration had been ameliorated. It seems likely that natriuresis in response to dehydration is common in mammals. We postulate that such a natriuretic response may serve a homeostatic function in buffering increases in plasma [Na] and osmolality that result from dehydration.

Binding of 125I-[Sar1,Ile8] angiotensin II (AII) to sections of brains from both wild and laboratory rabbits was determined by in vitro autoradiography. In the forebrain, specific high density binding was observed in the olfactory bulb, organum vasculosum of the lamina terminalis (OVLT), subfornical organ, median eminence, lateral septum, median preoptic nucleus and hypothalamic paraventricular, supraoptic and arcuate nuclei. In the midbrain, binding of the radioligand was observed in the interpeduncular and parabrachial nuclei, in the locus coeruleus, and ventrolateral pons. In the hind brain, there was dense binding of 125I-[Sar1,Ile8] AII to the nucleus of the solitary tract (NTS) and to both rostral and caudal parts of the reticular formation of the ventrolateral medulla oblongata. Weaker specific binding of the radioligand to the molecular layer of the cerebellum, to the nucleus of the spinal trigeminal tract, dorsal motor nucleus of the vagus, area postema, and to a band of tissue connecting the NTS to the ventrolateral medulla was also observed. Binding of the ligand to circumventricular organs such as the OVLT, subfornical organ, and median eminence suggests that these are sites in the brain of the rabbit at which blood-borne AII may exert influences on the central regulation of fluid balance and pituitary hormone secretion, although AII of neuronal origin could also act at these sites. Binding of the radioligand in several other brain regions suggests that angiotensin II of cerebral origin may be involved in a number of different aspects of brain function in the rabbit. The finding of dense binding in the NTS and ventrolateral medulla, which are involved in autonomic activity and are also sites of catecholamine-containing neurons, raises the possibility of angiotensin interaction with these neurons and involvement in autonomic function.

In view of the importance of Na+ equilibrium to normal function of higher species, an innate behaviour pattern promoting its intake in the face of deficiency could give an important survival advantage to the organism. Richter (1956) has shown that young rats, for whom their mother's milk has been the sole source of nourishment, consistently showed an active appetite for NaCl when confronted with it for the first time. He states that with mammals there is a universal liking for NaCl, and he considers this to be indicative of an inherited behaviour pattern which has conferred survival advantage. This primitive attraction for salt was modified by metabolic conditions, as is evidenced by the increased intake of NaCl solution which occurred when NaCl loss was caused by adrenalectomy.Previous publications from this laboratory have described the preparation and maintenance of sheep which have a permanent unilateral parotid fistula (Denton, 1956(Denton, , 1957 a; Denton, Goding & Wright, 1959), and lose 1-41./day of alkaline parotid saliva containing 170-680 m-equiv of NaHCO3. An animal prepared in this manner is an excellent subject for the study of physiological adaptations in the face of a controlled and precisely defined stress on the milieu interieur. This paper reports experiments on the voluntary intake by sheep of Na-containing solutions, and the effect of Na+ deficiency caused by loss of saliva on this voluntary intake. METHODSTwenty sheep of Merino or Merino cross-breeds were used. Six were ewes, the remainder were wethers. They were 1-7 years old. Apart from the normal sheep in Table 1 all had Wright-type permanent unilateral parotid fistulae and ipsilateral carotid artery loops. A number had contralateral carotid artery loops also. Three sheep, T.P. 1, T.P. 4, and T.P. 12, had the left adrenal gland transplanted to a combined carotid-artery-jugular-vein skin loop in the neck (McDonald, Goding & Wright, 1958) and the right adrenal gland removed.Most of the sheep were purchased from sale yards, and their previous history was unknown in relation to the possibility of access to salt licks or to bore water containing salt. The animals were kept in stainless-steel metabolism cages which effectively separated excreta, 7 PHYSIO. CLVII