The lowest vertebrata have parallel development of lymphatic and lymphoid systems on the basis of venous bed. Cyclostomes´ arteries invaginate into widening vein lumen. The side pockets separation in fish leads to formation of lymph tube (LT) net. At these stages of evolution defuse lymphadenoids contact with venous sinusoids. Reptiles and birds have inspissations of lymphoid tissue on sides of LT. Lymphatic and lymphoid systems convergate at periphery, where LT and blood vessels interweave. Their intervessel connective tissue is transforming into lymphoid around blood microvessels and appear surrounded by LT. Birds and mammals have the same formation of lymph nodes (LN). LN function as counter-current flow system: through LT antigens come to its substance, and through vessels - blood cells. Into parenchyma of the majority of lymphoid organs antigens, other immunogenesis excitors come not through LT but, for example, through tissue channels into tonsil crypto-lymphon. Progressive intensification of metabolism, speed of histogenesis and organ growing in vertebrate evolution lead to uneven growth and differentiation of vessel net, formation of LT and LN.
The work is presented for an International Scientific Conference "Innovation Medical Technologies", Russia (Moscow), November 17-18, 2009. Received by the editorship on 25.09.2009.