HIV and men who have sex with men sexual activity with members of the same sex, regardless of how they personally identify themselves. Many MSM choose not to (or cannot for other reasons) identify as homosexual or bisexual. Similarly, the label excludes men who identify as gay or bisexual, but who have never had sex with another man, including many gay teenagers. The terms MSM and women who have sex with women (WSW) have been used in medical scholarship since at least 1990. But, the term has been attributed to Glick "et al.", because their usage in a 1994 study solidified the concept in medical terminology. MSM is
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