The Cytology of the Mid-gut and Hepatic Caeca of Periplaneta orientalis

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Abstract
The observations here recorded on the general structure and arrangement of the epithelial cells of the mid-gut and hepatic caeca agree fairly closely with previous accounts for the cockroach; The hepatic Caeca and anterior region of the mid-gut are chiefly secretory, while the posterior part of the mid-gut is mainly absorptive in function. In the caeca and anterior part of the mid-gut periods of secretion alternate with periods of absorption. The secretory cells degenerate after a time, and are replaced by young cells which are at first, in all probability, absorptive in function. The mitochondria of the secretory cells are in the form of filaments in the basal region and in the neighbourhood of the nucleus; those between the nucleus and the lumen are usually granular. In certain cells most or all of the mitochondria are granular. The mitochondria of the absorptive cells are closely similar to those of the secretory cells. Mitochondria were identified in the replacement cells. The Golgi elements of the secretory cells are in the form of rods and granules; some of the curved rods enclose a lightly impregnated material; the elements are situated chiefly in the neighbourhood of the nucleus. The Golgi bodies of the absorptive cells are often smaller, and extend farther towards the lumen than do those of the secretory cells. Golgi elements were identified in the older replacement cells. It is suggested that material is separated out under the influence of the mitochondria, chiefly in the basal region of the cell, and that this material moves to the vicinity of the nucleus, where, under the influence of the Golgi elements, it is used in the formation of the secretory granules. Recent work having a bearing on the present investigation is discussed.

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