Chronic cervical lymphostasis was induced in cats. The effects in regions directly drained by lymphatics (facial skin and retrobulbar tissue), and in regions primarily drained by prelymphatics (cerebral cortex, retina, papilla, iris, choroid and Circle of Willis) were studied ophthalmoscopically and electron microscopically. It was found that in all regions there was considerable oedema, increases in protein concentration and excess collagen, together with increased numbers of macrophages. The lymphatics, where these existed, had many open junctions: both these vessels and the prelymphatics were very dilated, with considerable increases in protein concentration.

In rats fed a diet lacking flavonoids (but which had supplementary vitamin C) definite fine structural alterations were found in blood capillaries and tissues. These fine structural alterations were quite different from those reported in C-avitaminosis and imply a different deficiency. They were largely prevented by feeding the benzopyrones, coumarin or coumarin plus troxerutin, thus pointing to the specificity of the lesions. This implies that, for the rat, benzopyrones are vitamins and that vitamin C and "vitamin P"-deficiency states are qute distinct. In "P-avitaminosis" the basic lesion is the opening of some blood capillary endothelial intercellular junctions. Unlike in C-avitaminosis, the endothelial cells are intact, without pale, grossly swollen cytoplasms.

It has been shown previously, by plethysmographic measurements, that experimental lymphedema can be treated successfully by administration of coumarin and by massage. The present study confirms this fact by histological examination.

No abstract

1. External lymph drainage brings about a significant protective effect in thermal oedema of the rat hind leg. It is suggested that external lymph drainage prevents vasoactive substances drained from the site of injury from passing into the blood stream, which would further increase permeability of the injured blood capillaries.2. Coumarin (5,6-benzo-alpha-pyron) brings about a significant protective effect against the same injury in sham-operated rats.3. The strongest protective effect may be attained by combining external lymph drainage with the administration of coumarin.4. The additional therapeutic effect brought about by coumarin treatment in rats with external lymph drainage is not mediated by an increased flow. The possible mechanisms are discussed.