INTRODUCTIONThe ability of the adrenal cortex to regenerate has been observed by numerous workers. Graham ('IS) found that guinea pigs shorn necrotic cells in the adrenal cortex after chloroform anaesthesia for three hours and that repair of the damaged cortex is effected by mitotic ciivisioii of the surviving cells. Particularly the glomei-ulai-zone arid the outer portion of tlie fascicular zone appeared to constitute a growth centre from which regeneration look place. Vaccarezza ('45) concluded that local replacement of cells could take place in all parts of the cortex. Gi-ec.p and Deane ('49a) showed that regeneration of the rat adrenal was possible after enucleation, starting in this instancfl from cells adjacent to the capsule. Schaberg ( '51, '52) observed regeneration of the adrenal cortex in patients who snrvived an acute fulminating disease for some days. It was suggested that under these conditions regeneration took place from the capsule and the peripheral part of the cortex.The purpose of this investigation was to develop a technique which would enable us to study these regenerative processes in vitro as opinion apparently is still divided regarding the site of regeneration and the relationship between the different zones of the adrenal cortex.
METHODAdrenal glancls mere obtained from 5-day-old rats. The surrounding tissue was removed and the gland cut with the aid of a dissecting microscope into 5-8 small fragments measuring between 0.3 and 0.5 mm. The fragments of one adrenal were then placed on the top of a coagulated niedium and the container ivas closed with a glass plate drenched in heated paraffin ( fig. 1) and incubated at 37 "C. (Gaillard, '51). Every third day the explants were removed from the clot, to which they adhere by outgrowing cells, washed in saline and transferred to a freshly prepared cup. In each series a litter of 5-10 rats was used enabling double the number of cups to be set up at one timc. -kt two t o three day intervals the fragments iii one cup were fixed in Bouin's solution, embedded in paraffin, cut in serial sections and stained with heniatoxylin and eosin. I n this may development of the cultures mas followed over a 4-week period. I n each series the adrenals of one rat were used as controls.I n preliminary experiments we used a medium as suggested by Martinovitch ('51) which mas coniposed of rat plasma 7 parts, chicken plasma two parts and chiclieii embryo extract 8 to 10 parts. This proved disappointing but after some trial and error satisfactory results were obtained with a more homologous medium consisting of brain extract and adult rat plasma. The brain extract was prepared from two to three wceks old rats from the same strain as those of which we used the adrenals. This choice was based on the findings of Gaillard ('42) that the histological structure of tissucs can best be retained by cultivation in a medium with a press juice from animals of the same age o r a little older. The brains were removed aseptically, cut in small pieces and placed in a petri dish at...
