ABSTRACT
An account is given of some characteristics of the pancreatic islet tissue of the frog, based largely on material fixed in Helly’s fluid and subsequently postchromed. It is shown that the cells, which superficially differ greatly amongst themselves in appearance, can be interpreted as representing stages in a single secretory cycle, and cannot be readily differentiated into the entirely distinct cell types which have commonly been thought to characterize the islet tissue of other vertebrates. Secretory activity centres round an organelle which is believed to be the true ‘specific granule’, and which is formed by the condensation of chromophil material within a chromophobe body. The latter develops a sudanophil rim which is also a characteristic feature of the specific granule itself, the secretory activity of the latter involving an intense lipoid metabolism and being accompanied by a reduction of chromophilia. These observations cannot at present be readily related to the traditional descriptions of the ‘A’ and ‘B’ (and more recently ‘D’) cells, although the specific granule in the earlier stages of its activity appears to resemble the ‘A’ granule of other vertebrates in its staining reactions. Certain reactions characteristic of ‘B’ and ‘D’ granules can also be recognized, but it is too early to evaluate these with confidence. The observations are discussed in the light of current views on the cell-inclusions, particular attention being drawn to the similarity which the chromophobe bodies bear to Golgi spheroids (lipochondria), both in their appearance and in their apparent ability to segregate material from the surrounding cytoplasm.
