Summary. Changes in the concentration of IgG^. IgC,, IgM, IgA and albumin in semm and mammary secretion were studied in 15 cows and 2 heifers before and after parturition. Concentrations of IgGj and IgC, in blood serum 3-5 weeks before parturition were 13-38 ± 0-75 and 10-08 ±: 0 39 mg/ml (means ± S.E.) respectively. In all animaLs tlie cfinc-entration of IgC, in serum decreased abruptly, usually by more than 50%, 2-3 weeks before parturition, and during the same period the concentrations of IgC2, IgM, IgA and albumin in seriun remained unchanged. Four weeks after parturition the concentration of IjiC, in serum had returned to values similar to tho.se observed prior to the abrupt fall.Five weeks before parturition the concentration of IgGj in mammary secretion was, on average, 11 times higher than that of IgC^. Highest concentrations of IgGj in secretion (113-89 rt 11-41 nig/ml) were obser^-ed 2-3 vi'eeks before parhirition in 16 of the 17 animals. The concentration of IgG., over the 5 weeks prior to parturition remained unchanged at levels of approx 30X of comparable values in seruui. Concei trations of IgM (11-8.^ ± 0-53) and IgA (3-80 it 0-20) in secretion collected prior to antl immediately afler parturition were, on average. 2 and 7 times higher respectively than those in serum."Hie sharp fall in the concentration of IgG, in serum in the absence of any suggestion of a concomitant decrease in IgGg concentration .strongly suggests that the degradation hypothesis proposed by Brambell (1958Brambell ( . 1966 for selective transfer of protein across epithelial membranes does not hold for the mammary gland of the cow. The results support an allernative hypothesis based on the existence of IgGj-specific receptor sites located on the basal or intercellular membrane of the glandular epitlieL'al cells.

Surgical techniques for collecting lymph from the thoracic, hepatic, intestinal and mammary lymph ducts of sheep are described. Recirculating thoracic and intestinal lymph fistulhe were maintained for periods of up to 2-3 weeks. At the end of this time the sheep were in good condition and had lost little weight.Liver lymph was collected for 2-3 weeks and mammary lymph for periods up to 10 weeks. The lymph from these preparations was collected into a plastic bottle sutured to the animal's flank. The sheep with hepatic lymph fistule showed a loss in weight after about 7-10 days but remained in good health for 2-3 weeks. The drainage of lymph from the udder for periods up to 10 weeks had little effect on the general condition of the sheep.IN order to study various aspects of lymphatic physiology, it is necessary to obtain animal preparations from which lymph can be collected over relatively long periods of time under physiological conditions. Bollman, Cain and Grindlay [1948] described a method of collecting thoracic duct, liver and intestinal lymph from unanaesthetized rats over a period of several days.This technique has been used extensively to study various aspects of fat digestion and absorption, the factors which affect the production and flow of lymph, the physiology of the lymphocyte and the exchange of various substances between blood and lymph. In the case of the thoracic duct, this technique provides a simple and reliable method for the collection of lymph for periods of several days. The small volume of lymph which comes from the liver and the low rate of flow makes the long term collection of liver lymph in the rat relatively difficult. In addition, the small blood volume of the rat restricts the volume of blood samples and the frequency with which they can be taken.The dog has been used as an experimental subject for the collection of lymph by several groups of workers [Cain, Grindlay, Bollman, Flock and Mann, 1947;Glenn, Cresson, Bauer, Goldstein, Hoffman and Healey, 1949;Grindlay, Cain, Bollman and Mann, 1950;Brown and Hardenbergh, 1951;Rampone, 1959]. The use of trained dogs, together with various methods of restraint such as plaster jackets and collars, has allowed the collection of lymph from thoracic and hepatic lymph ducts in unanoesthetized animals. With the exception of the method described by Brown and Hardenbergh [1951], all the techniques in which rats or dogs have been used lead to a drastic loss of weight due to the continuous drainage of large amounts of proteins, fluid and electrolytes from the lymphatic fistul,e. Brown and Hardenbergh [1951] attempted to overcome the effects of continued lymph

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