Men who have sex with men with regard to trans women, people born either biologically male or with ambiguous genitalia who self-identify as female. Some sources consider trans women who have sex with men to be MSM, others consider women who are trans "alongside" MSM, and others are internally inconsistent (defining transgender women to be MSM in one place but referring to "MSM and transgender" in another). Determining the number of men who have ever had sex with another man is difficult. Worldwide, at least 3% of men, and perhaps as high as 16% of men, have had sex at least once with a man. These
Lymph hearts pumps lymph into the jugular vein. The other pair at the end of the vertebral column pump lymph into the iliac vein in the legs. "Rana catesbiana" and "Rana nigromaculata" have mast cells in the lymphatics of the tongue. These are round and in the monocellular layer of the lymphatic walls either in close adhesion or in contact with the cytoplasmic process. The lymph hearts rhythmically and slowly pump to drive the lymph into the veins. It is possible to see the lymph hearts beat by looking on the dorsal surface on either side of the urostyle. In the toad