1. 1. A detailed study and a completed picture is drawn from the available embryologic data describing the anterior abdominal wall. 2. 2. The average and variational types of the component parts of the abdominal wall are detailed and depicted, and their effect upon potentiality for hernia analyzed. 3. 3. There are advanced: 3.1. (a) An explanation of the mechanism of formation of the linea semilunaris. 3.2. (b) A reason for the belief that one of the causes of non-descent of the testicle is mechanical obstruction. 3.3. (c) A concept of the anterior abdominal wall as a bridge construction of multiple arches, the mechanism and function considered as potential factors in the causation of hernia. 3.4. (d) A concept of the conjoined tendon as the middle pier of support of the anterior abdominal wall. 3.5. (e) A reason why more hernias do not occur when the area of muscle deficiency is largely increased from the average. 3.6. (f) An explanation of reciprocal compensatory action of the entire abdominal wall as a preventive of hernia.