Scanning electron microscopy on the distribution of the minute blood vessels in the thyroiod gland of the dog, rat and rhesus monkey.

Using corrosion casts prepared with methyl methacrylate (MURAKAMI, 1971), the distribution of minute blood vessels in the thyroid gland of the dog, rat and rhesus monkey was observed with the scanning electron microscope. The blood capillaries derived from the interlobular or interfollicular arteries make a complex network encapsulating each follicle like a basket. In most follicles, capillaries for one follicle are well ramified and anastomosed with one another, and in a few follicles the anastomoses are not so well developed. In the dog and rat the wall of each basket consisting of the capillary network is often common with that of the adjacent follicles. Two rooms surrounded by perifollicular capillary networks are often connected with one another like Siamese twins. By transparent electron microscopy, follicular epithelial cells of the adjacent two follicles are sometimes in contact directly without any connective tissue between them. In the monkey, the capillary network of one basket is completely independent of that of the adjacent one and a round or oval complete structure like a basket ball is characteristic.