Abstract
In the present paper studies were made to inv<pstigate the mesenchymal or con-.< nective tissue haematopoiesis with some observations in reference to the formationof Iymphocytes in the lymphatic tissues, i. e. the thymus and Nymph nodes, and tosupplement the studies on the intra-embryonic haematopoiesis of the cattle foetusin connection with the previous papers.The results obtained are summerized as follows :1) In the 9 am foetus, the smallest of the materials used, the appearance oflymphocytes in the thymus is clearly noted.In the 14 cm foetus, the Nymph nodes -superficial cervical and popliteal node-which could not be observed in younger foetuses, presented, already, the appea-rance of lymphocytes.2) In foetuses ranging from 24.5 to 58 cm, the haematopoietic foci composedof granulocytes, and partially of erythroblasts, are observed in the interstitial con-nective tissue of the thymus, especially they could be observed more clearly in theolder foetuses in which granulocytes are also found in the parenchyma.3) Using the superficial cervical and the popliteal nodes of foetuses rangingfrom 14 to 25 cm and the hepatic node of those ranging from 28 to 58 cm, thehaematopoietic foci composed of granulocytes, partially of megakaryocytes and ery-throblasts, are observed clearly in the hilus connective tissue and the parenchymaof the older foetuses.4) The haematopoietic foci of erythroblasts are observed in the followingtiessues : the adrenal medu11a= and capsule, the renal stroma, the pancreatic con-nective tissue, and the juxta-femoral connective tissue in 9 am foetus, and the con-nective tissue near the fourth thoracic vertebra in 6.7 cm foetus.5) In regard to the time of the first appearance of lymphocytes in the thymusand Nymph nodes, further studies on the younger foetuses are to be recommen-ded. Since many authors report in regard to haematopoiesis of other mammalsin many sites where the mesenchymal or connective tissue haematopoiesis is found, it is necessary to study more extensively the cattle foetus in regard
