1 Introduction.- 1.1 Experimental Diabetes in the Sand Rat.- 1.1.1 Zoology.- 1.1.2 Physiological Characteristics.- 1.1.3 Types of Diet-Dependent Diabetes Development.- 2 Aims of the Study.- 2.1 Islet Cytology.- 2.2 Islets of Langerhans and Other Endocrine Organs in Diabetes Mellitus.- 3 Materials and Methods.- 3.1 Animal Housing.- 3.2 Animal Preparation and Investigation.- 3.2.1 In Vivo Experiments.- 3.2.2 In Vitro Experiments.- 3.2.3 Tissue Extraction and Analysis of Metabolites.- 3.3 Histological Methods.- 3.4 Cytochemical Methods.- 3.5 Electron Microscopy.- 3.6 Morphometry.- 3.6.1 Islets.- 3.6.2 Adenohypophysis.- 3.6.3 Adrenal Cortex.- 3.6.4 Thyroid.- 3.6.5 Gonads.- 3.6.6 Statistics.- 4 Islets.- 4.1 Islet Cytology.- 4.2 Innervation of the Pancreas and Islets of Langerhans.- 4.3 Islets of Langerhans in Diabetes Mellitus.- 4.4 Insulin Secretion of Islets of Langerhans.- 4.5 Insulin Resistance of Insulin-Sensitive Tissues.- 4.6 Influence of Stress on Insulin Resistance of Glucose Utilization and Hyperinsulinemia.- 5 Role of Other Endocrine Organs in Diabetes Mellitus.- 5.1 Adenohypophysis.- 5.2 Adrenal Cortex.- 5.3 Thyroid.- 5.4 Testicles.- 5.5 Ovaries.- 6 Conclusions.- 7 Summary.- References.