The Study of the Snake Form (蛇形學) from The Study of Xing Yi Quan (形意拳學)

蛇形學

蛇形者，乃天地所賦之性，身體最玲瓏，最活潑者也。身形有撥草之能。二蛇相斗，能泄露天之靈機，能曲能伸，能繞能蟠。在腹內卻為腎中之陽，在易即為坎中之一也，在拳中謂之蛇形。能活動腰中之力，乃大易陰陽相摩之意也，又如易經方圖之中，震巽相接，十字當中求生活之謂也。其拳順則內中真陽透於外，如同九重天，玲瓏相透，無有遮蔽，人之精神如日月之光明矣。其拳謬則陰氣所拘，拙勁所綑，身體不能活潑，心竅亦不能通靈矣。學者於蛇形中勉力而行，久之自能有得。如蛇之精神，靈巧奧妙，言之不盡。

孫祿堂

"The snake is endowed with the most nimble and lively body in nature. It is able to move through the grass. The view of two snakes fighting exposes the ingenuity of nature: it can bend and stretch, coil and curl. Within the abdomen, it is the Yang aspect of the kidneys. In the Book of Changes, it is one with the trigram Kan. In boxing, it is called the snake form. It is the ability of a movable waist and therefore it means the rubbing of the Yin and the Yang from the Book of Changes, looking like the interlocking of the Zhèn and Xùn hexagrams in the square diagram, the crossover at the center that represent the generation of life. If the boxing is performed conveniently, then the real internal Yang aspect will reveal itself outwardly, like the nine levels of the sky delicately passing through each other without obstruction, one’s vitality like the radiance of the sun and the moon. If the boxing is performed erroneously, the Yin Qi will be restrained, the clumsy Jin will be tied up, one’s body will not be lively and the mind will not be able to perceive clearly. Students of the snake form that persevere may grasp it after a long time, and as in the vitality of the snake, they will be nimble beyond words."

From the book The Study of Xing Yiquan (形意拳學), by Sūn Lùtáng (孫祿堂), based on the translations by Albert Liu and Dan Miller and Brennan Translation Blog