Girth (tack) strip down its center, it may cause discomfort. It is also best if it has some "give" to it, which makes it more comfortable for the horse. Many riders also choose a girth that allows for extra elbow room, so the horse is not restricted as his leg moves backward. To measure for a girth, the saddle with a pad should be placed on the horse. A measuring tape is then used to measure from the middle hole of the billet on one side, under the horse's belly, to the middle billet on the other side. If a girth is
Animal testing on invertebrates studies on social behavior. General Practical Animal testing on invertebrates Most animal testing involves invertebrates, especially "Drosophila melanogaster", a fruit fly, and "Caenorhabditis elegans", a nematode. These animals offer scientists many advantages over vertebrates, including their short life cycle, simple anatomy and the ease with which large numbers of individuals may be studied. Invertebrates are often cost-effective, as thousands of flies or nematodes can be housed in a single room. With the exception of some cephalopods, invertebrate species are not protected under most animal research legislation, and therefore the total number of invertebrates used remains unknown. Research on invertebrates is