It is difficult that we understand "Due to pathogenic Gi(因於氣)" in "Somun(素問) Saenggitongcheonron(生氣通天論)", because that is too many comments. We are to interpret Gi(氣) as Wind(風) or Anger(怒). However, the most reasonable explanation is to Yang-Gi weakness(陽氣虛). In other words, pathogenic Gi of four seasons should violate Yang-Gi(陽氣) and become a Yang-Gi weakness. Sayu(四維) can be interpreted as limbs[四肢], the last month of each of the four seasons[四季], four seasons[四時]. It is a logical view of the four seasons. This meaning is that it was already Yang-Gi weakness state by pathogenic-Gi of four seasons which violate Yang-Gi(陽氣), again the pathogenic Gi of four seasons violate Yang-Gi. As a result Yang-Gi will drain.