Cleavage line patterns of the skin in the horse

In 6 equine specimens of both sexes, the morphological features of the cleavage lines of the skin over the entire body were examined using a metal probe with a sharp conical point. Wounds were produced on the skin with the probe and painted with Chinese white or Indian ink. The direction of running of the cleavage lines was determined from their relationship to the long axis of each region or area of the physical structure. The cleavage lines of the head and face revealed a fixed pattern in all specimens. They were similar to those of equine fetuses of 6 to 7 months of age. A transverse pattern was found on the skin of the neck, trunk (abdomen), roots of the ear and tail, and external genital labium, except in some localized areas. The cleavage lines of the free extremities of the appendages already displayed a strikingly longitudinal pattern. A horizontal pattern was found in the middle costal region. It was clearer in the adult horse than in the equine fetus. The cleavage lines were annular in arrangement on the skin around the nares, eyes, and preputial orifice. They showed a convergent pattern on the skin of the metacarpal and metatarsal calcars, the umbilicus and anus. Some aspects of the skin tension were compared between the horse and certain other animals.