For this reason, I thought it appropriate as we reflect on our Lord’s passion this day to be reminded of just what all He endured on our behalf. The following piece has been adapted from C. Truman Davis, M.D. in The Expositor's Bible Commentary, Volume Eight: Matthew, Mark, and Luke...
A medical doctor provides a physical description: The cross is placed on the ground and the exhausted man is quickly thrown backwards with his shoulders against the wood. The legionnaire feels for the depression at the front of the wrist. He drives a heavy, square wrought-iron nail through the wrist and deep into the wood. Quickly he moves to the other side and repeats the action, being careful not to pull the arms too tightly, but to allow some flex and movement. The cross is then lifted into place.
The left foot is pressed backward against the right foot, and with both feet extended, toes down, a nail is driven through the arch of each, leaving the knees flexed. The victim is now crucified. As he slowly sags down with more weight on the nails in the wrists, excruciating, fiery pain shoots along the fingers and up the arms to explode in the brain; the nails in the wrists are putting pressure on the median nerves. As he pushes himself upward to avoid this stretching torment, he places the full weight on the nail through his feet. Again he feels the searing agony of the nail tearing through the nerves between the bones of his feet.
As the arms fatigue, cramps sweep through the muscles, knotting them in deep, relentless, throbbing pain. With these cramps comes the inability to push himself upward to breathe. Air can be drawn into the lungs but not exhaled. He fights to raise himself in order to get even one small breath. Finally carbon dioxide builds up in the lungs and in the blood stream, and the cramps partially subside. Spasmodically he is able to push himself upward to exhale and bring in life-giving oxygen.
Hours of this limitless pain, cycles of twisting, joint-rending cramps, intermittent partial asphyxiation, searing pain as tissue is torn from his lacerated back as he moves up and down against the rough timber. Then another agony begins: a deep, crushing pain deep in the chest as the pericardium slowly fills with serum and begins to compress the heart.
It is now almost over; the loss of tissue fluids has reached a critical level; the compressed heart is struggling to pump heavy, thick, sluggish blood into the tissues; the tortured lungs are making a frantic effort to gasp in small gulps of air.
He can feel the chill of death creeping through is tissues... Finally he can allow his body to die. All this the Bible records with the simple words, "And they crucified Him." (Mark 15:24).
One cannot help but marvel at all of this! What wondrous love is this? That the God of all the universe would clothe himself in human flesh and come into this world in order to endure just such torment. He did not have to do this. Rather He chose to do this!
Little wonder the Apostle John was moved (in his First New Testament General Epistle, chapter 3, verse 1) to write these words: “Behold what manner of love the Father has given to us, that we should be called children of God.”
SOURCE: The Expositor's Bible Commentary, Volume Eight: Matthew, Mark, Luke (Zondervan, 1984).
This illustration is also been reproduced in several places online. See, for instance: https://www.sermonsearch.com/sermon-illustrations/1279/crucifixion-described/.
SCRIPTURE SOURCE: http://biblehub.com/1_john/3-1.htm.
NOTE: For a much more extensive article of the process of crucifixion, check out the article titled “On the Physical Death of Jesus Christ” by William D. Edwards, MD of the Mayo Clinic Department of Pathology and Floyd E Hosmer, MS, AMI of the Mayo Clinic Department of Medical Graphics, Rochester, Minn. and the Homestead United Methodist Church, Rochester, Minn., and Pastor Wesley J. Gabel, MDiv of the West Bethel United Methodist Church in Bethel, Minn. It was first printed in JAMA - The Journal of the American Medical Association, March 21, 1986, Volume 256.
The complete article, with extensively detailed illustrations, has been reprinted here in pdf form: http://people.bethel.edu/~pferris/ot103/Jesus_Crucifixion.pdf.