“ST. Luke’s Greek text is more exact: “Egeneto o hidros autou ôsei thromboi aimatos katabainontes epi tèn gèn” Now, thrombos means a clot. These clots have always presented translators with difficulty; they quite rightly say that clots cannot come out of a body. And thus they have set out to do violence to the words, because they do not understand the physiological phenomenon. Some ancient manuscripts have gone further still and have suppressed the passage, as if it was unworthy of the Divinity of Jesus. Father Lagrange, who was a most attractive exegetist, but not a doctor, translates it ‘like globules of blood, running right down to the ground.’
“Now, this phenomenon, which is known in the profession as hematidrosis, consists of an intense vasodilatation, of the subcutaneous capillaries. They become extremely distended, and burst when they come into contact with the millions of sweat glands which are distributed over the whole skin. The blood mingles with the sweat, and it is this mixture which pearls over the whole surface of the body. But, once they reach the outside, the blood coagulates and the clots which are thus formed on the skin fail down on to the ground, being borne down by the profuse sweat. St. Luke thus proved himself to be a good doctor and a good observer when he wrote: ‘And His sweat became as clots of blood, trickling down upon the ground.’
— Pierre Barbet, M.D., A Doctor at Calvary (Image Books, 1963); p. 88