fonalitÃ© | Flickr. American Express uses the first two numbers of the card to identify itself. That two-digit number will be either 34 or 37. The third and fourth digit signify the type of card and the currency being used, according to Clearpoint Credit Counseling.
Formed Elements of the Blood. the solid fraction of the blood, consisting of erythrocytes, leukocytes, and thrombocytes. The formed elements constitute up to 40 percent of the volume of the blood in lower vertebrates (fishes, amphibians, and reptiles) and up to 54 percent in higher vertebrates (birds and mammals, including man). The most numerous among the formed elements of the blood are the erythrocytes, which contain hemoglobin. They transfer oxygen from the respiratory organs to the tissues and help transfer carbon dioxide in the opposite direction.
Blood Constituents. Blood consists of blood cells and plasma. If blood is treated with an anticoagulant and centrifuged, the blood cells sediment leaving a supernatant of clear plasma. Blood Cells. The sedimented blood cells account for 35-50% of the volume of blood and are of three basic types. erythrocytes or red blood cells; leucocytes or white blood cells