CYTOLOGICAL CRITERIA OF MAMMALIAN ENDOCRINE ACTIVITY

A CONSIDERATION of the development of endocrine histology throws considerable light both upon the problems which have confronted the investigator and the way in which attempts have been made to solve them. When the physiological significance of the endocrines was less understood than it is now, their histological descriptions were relatively simple. For example, in the anterior lobe of the pituitary two chromophilic and one chromo-phobic type of cell were described. As the gland came to be investigated in the light of an increasing knowledge of its physiological activities and with improved techniques, the complexity of the histological picture increased. Transition cells between chromophobe and chromophil have been recognized in many animals investigated1*2'3, and in the dog4 dark and light varieties of the basophil cells have been described, as have special carmine acidophils in the cat5. In a like manner, the original principal and oxyphil cells of the human parathyroid6*7 have each been divided into two types-dark and light; osmiophilic and non-osmiophilic cells have been described in what was originally considered as the uniform parenchyma of the rat parathyroid8*9, and I10 have observed a somewhat similar differentiation with intermediate cell types in the mouse. Again, in the human pancreatic islets Gomori11 has recorded cells intermediate between A -cells and the D-cells of Bloom, and Hoerr12 and others have described dark and light cells in the zona reticularis of the adrenal cortex.