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In paired tests obtained from 425 adults, 50 children and 10 neonates, the incidence of testicular appendices was 76% in adults (93.3% sessile) and 83.3% in neonates/children (88% sessile). An epididymal appendix was present in 21.9% of adults and 20% of neonates/children, out of which 79% were stalked in both types of specimen. Three sessile testicular appendices and 11 epididymal appendices were double. The microscopic structure of the appendices and the ultrastructure of their epithelia are described. Testicular or epididymal appendices were not present in any domestic or laboratory animal examined except the horse.

Fine anatomical structures of the different regions (viz., anterior, middle and posterior) of the intestinal mucosa in adult Labeo rohita (Hamilton) have been studied by using Scanning Electron Microscope (SEM). Surface mucosal modifications of the anterior and the middle of the intestine not only increase the luminal surface by 2-4 times but serve also the storage function of the ingested food due to the absence of stomach in the fish studied. Fine anatomical structures of the columnar epithelial and goblet cells of the mucosa have been studied in detail. The height and complexity of the microridges on the luminal end of each columnar cells in the various regions vary greatly probably due to the functional variations of the region concerned. Communication between the columnar cells and the sub-mucosal layer through the basement membrane is effected by circular orifices. A pear-shaped apical portion provided with prominent microridges of the goblet cell probably allows the mechanical stress to develop for the accumulation of secretory mucins.

Colonocyte damage in the rectal mucosa in shigellosis is the result of bacterial invasion and leads to ulceration. Additional factors in colonocyte damage may be the Shigella cytotoxin and, especially in colonic crypt cells, bacterial endotoxin. A vascular lesion was present in the lamina propria of the rectal mucosa, which resembled endothelial damage secondary to bacterial endotoxins. In patients with longer duration of symptoms, relative vascular insufficiency, activated lymphocytes, eosinophil and mast cell degranulation, and antibody-mediated colonocyte damage may all play a role.

The ultrastructure of the jejunal mucosa obtained by peroral biopsy from 7 control subjects and 12 patients with tropical sprue was studied. Compared with biopsies from control subjects in temperature zones, southern Indian control subjects showed minimal increase in lysosomes in surface epithelial cells, an occasional dark-staining degenerating epithelial cell in the upper two-thirds of villi, and an increase in cellular infiltration of surface epithelium and lamina propria. The jejunal epithelial cells of tropical sprue patients had abnormal microvilli, marked increase in lysosomes, increase in intracellular fat, and degenerative changes in rough endoplasmic reticulum and mitochondria. Two types of degenerating epithelial cells, designated pale and dark based on their staining quality, were seen in the villi. Pale staining degenerating cells were also seen in the crypts. The basement membrane region showed an amorphous deposit with many collagen fibers and fat droplets. The epithelial layer and lamina propria showed increased cellular infiltration. In one biopsy from a patient with sprue, particles of possible viral origin were seen.