Sentence:  For they considered the odd numbers as male and the even ones as female , equating the two groups with the Yang and Yin principles in Nature ; and in this square , the respective pairs made up of large and small odd ( Yang ) numbers , and those <WSD>composed</WSD> of large and small even ( Yin ) numbers , were all equal to each other . 
Meaning of the word marked with <WSD> tags:  form the substance of