~10^10 lymphocytes: lymphocytes' mean blood transit time 25±6 min lymphocytes/day
||Human Homo sapiens
||Pabst R. The spleen in lymphocyte migration. Immunol Today. 1988 Feb9(2):43-5. DOI: 10.1016/0167-5699(88)91258-3 p.43 right column top paragraphPubMed ID3256315
|| Trepel F. Number and distribution of lymphocytes in man. A critical analysis. Klin Wochenschr. 1974 Jun 1 52(11):511-5.  Schick P, et al., Autotransfusion of 3H-cytidine-labelled blood lymphocytes in patients with Hodgkin's disease and non-Hodgkin patients. II. Exchangeable lymphocyte pools. Acta Haematol. 1975 53(4):206-18.PubMed ID4853392, 808930
||P.43 right column top paragraph: "In man, the circulating blood contains about 10^10 lymphocytes [primary source 14], which have a mean blood transit time of 25±6 min [primary source 15], resulting in an exchange rate of 48 times per day (about 5.0×10^11 lymphocytes) (Fig. 1). The daily recovery of lymphocytes from the thoracic duct in man is only about 3×10^10, equivalent to about 6% of the daily emigration of lymphocytes from the blood [ref 16], so most must leave the blood by routes other than the lymph nodes."