Alarm

Within six to forty-eight hours of the injury, the rats displayed a rapid decrease in the size of the Thymus, Spleen, Lymph Glands and Liver; loss of fat; Oedema formation; loss of muscle tone; fall of body temperature; formation of acute erosions in the digestive tract, particularly in the stomach, small intestine, and appendix; loss of cortical lipoids and adrenaline secreting cells from the adrenal medulla; sometimes increased blood flow to the skin; exophthalmos; and increased lachrymation and salivation; in particularly severe cases there was focal necrosis of the liver and dense clouding of the crystalline lens.

Resistance

About 48 hours after the injury Selye found that the adrenal glands were still enlarged, but there had been some recovery of the cortical lipoids, there was a large number of hormone producing cells in the pituitary, the thyroid gland had grown by producing new cells; however, body growth stopped and the gonads had become atrophic.

Selye prolonged the animals' stress by giving repeated doses of the drug over a period of 1-3 months. He found that the rats were able to build up a resistance to the stress and the organs appeared to return to normal.

Exhaustion

Selye found that after the resistance period, the rats were unable to maintain their stress defences. They began to develop symptoms that were similar to those in the first stage. Selye considered this to be due to exhaustion.

The results of these experiments led Selye to propose the General Adaptation Syndrome.