Quarterly Journal of Microscopical Science, Vol s3-91, 45-61, Copyright © 1950 by Company of Biologists

The Physiology of the Alimentary Canal of Tyroglyphus farinae

¹ Department, Birkbeck College, University of London

1. The pH of the stomach and its caeca lies between 5.0 and 6.0, that of the colon changes to the alkaline side of 7.0 but remains below 8.0. The pH of the post-colon is between 7.0 and 8.0. All these measurements are subject to protein error.

2. The stomach and its caeca are regions of:

(a) absorption;

(b) secretion of a mucus containing a digestive enzyme;

(c) digestion of carbohydrate and protein.

3. The optimum pH of carbohydrate digestion is 5.4 and of protein digestion5.6±2

4. The thin-walled colon regulates the pH of the food bolus and is the site of formation of a peritrophic membrane and some absorption.

5. The post-colon is the site of further absorption of water and solidification of the faecal pellet.

6. Excretory substances are first recognizable in the colon; they do not appear to be produced by the Malpighian tubules or post-colon.

7. The chief nitrogen katabolite is guanine.

8. There is an accumulation of nitrogenous katabolites in the parenchyma of the body in animals on a high-protein diet.

9. The powers of excretion of nitrogenous waste appear to be poor.

10. The main food reserves are of glycogen in the parenchyma; fat is not stored to any extent.

11. The salivary glands produce a mucus which serves as a lubricant for the food in its passage through the pharynx and oesophagus.