The appearance of a yellowish coating, turning progressively darker brown, and possibly almost black is a major pointer to the hæmolytic stage of Addison`s disease.

This is not the brown melanotic stain of the skin - which sometimes is found in the mouth. This is a substance which Charles Douglas Wehner has found can be scraped off the tongue by withdrawing it between the teeth.

It is caused by a shortage of hydrocortisone (see right). Hydrocortisone comes from the Zona Fasciculata - the middle of the three active layers of adrenal cortex, under the orange coating.

In the absence of hydrocortisone the metabolism cannot combust sugar. Protein - particularly that from the blood - is combusted in order to sustain life. The iron-bearing waste product hæmosiderin (hemosiderin) is discarded in body fluids, including saliva. Hence Addison`s first report on Anæmia, disease of the Supra-renal capsules.

Here are some documented reports:

Addison, p.17	"The tongue today is dry, and beginning to be sordid, teeth dirty".
Addison, p.35	"...tongue injected at the tip and edges, coated with a light brown fur, very dry."
Addison, p.36	"His tongue continues dry and coated with a brownish fur."
Greenhow case 98	"tongue red, covered with yellow fur;"

Hæmosiderin is made up of a large number of transferrin groups as shown on the left. The symbol Fe represents the iron.

A standard test for iron is the Prussian Blue test. This uses potassium ferrocyanide, which is not a deadly poison like potassium cyanide. However, it is not wholesome to eat.

First we must get rid of the protein to liberate the iron.

Veterinarians may take a spatula and scrape the substance off the tongue of the dog. Then they can put it in a test-tube and add a single drop of concentrated suphuric (sulfuric) acid. Be careful to avoid the acid spitting.

Still taking care, neutralise by adding an alkali. Then add potassium ferrocyanide.

The result - ferric ferrocyanide - is the well-know Prussian Blue. It is destroyed by both acid and alkali. However, if the pH is right a conspicuous blue colour should appear - signalling the presence of IRON.

This test - when applied to a dog - is a very strong indication of Addison`s disease.

The creation of a convenient device for the detection of hæmosiderin can be seen to be a major step towards the correct diagnosis of Addison dogs. Charles Wehner applied some thought to this, and realised that there are proteolytic enzymes discovered originally in deep-sea bacteria, which are used in the making of biological washing powders.

Construction would consist of a pod containing a mixture of proteolytic enzyme, of salts like common salt (NaCl) to act as buffers, and of potassium ferrocyanide. There would also be a hard edge to the device,which can be scraped gently along the tongue as a spatula.

In use, the device would be applied to the tongue and then bent and crushed to release the reagents from the pod. After a standard delay, perhaps a couple of minutes, to allow the reaction to come to completion, the device would be inspected. White - possibly magnesium-white - paper or plastic as a backing would help display the Prussian Blue result.

Such a device would be of interest to veterinarians and human doctors. Let us hope somebody decides to manufacture this.