Abstract
1. There are recognized many mast cells aggregating in the sinus of rat's lymphnode.
2. These cells appear to be of young type on the basis of their staining characteristics in azan and in astra blue-safranin O mixture. Their origin is supposed to be reticular cells of the lymphnode.
3. They are large in number in the cervical and thoracic lymphnodes, whereas few in axillary, inguinal and other lymphnodes.
4. Although it is generally considered that the mast cells increase in number as the host grows into senile stage, the mast cells in the lymphnode sinus are maximum in number in estrus stage.
5. The mast cells are present in the lymphnode sinus also in the mouse, rabbit, guinea pig, cat, dog, monkey and human.
