"Sunbursts" and "christiesomes": cellular fragments in normal cow and goat milk.

Goats' milk includes numerous cell fragments ("christiesomes") which originate from the mammary secretory cells, contain well preserved endoplasmic reticulum, mitochondria and lipid droplets, and are responsible for the considerable triglyceride synthesising capacity of fresh goat milk. Cows' milk shows a few such particles only after repeated oxytocin-aided milkings. Cows' milk does contain quite different particles which have a dense content with a few small vesicles and numerous microvillus-like protrusions on one side ("sunbursts"). These have not been found in goats milk. Cytoplasmic particles similar to sunbursts have been found on the surface of the mammary secretory epithelium. It is suggested that they are residues of dead cells.