In Reply.—I appreciate the thoughtful comments by Dr Schindler. I concur with his statement that the conclusion of the study would not surprise many grandmothers. I should also add that our choice of nipple units in bottle-feeding neonates is not based on physiologically relevant data.
Hole sizes were measured at zero transmural pressure. It is very likely that the hole size at the applied negative pressure is slightly larger than that at atmospheric pressure. I explicitly stated in the article that distensibility of the nipple, was not determined. Nipple thickness at the tip is only an indirect measure of distensibility at best, especially since composition of the materials used is not the same in all nipple units. However, differences in distensibility in a given nipple type are unlikely to account for most of the observed variability since the thickness and applied pressure are similar.
The mechanical drilling process used in the