Vol. 151, No. 4, April 1, 2019. 10.1085/jgp.201812274.
After publication, we discovered that there was an error in the units of the pump rate (p) in the legend to Figure 2 and in the x-axis label in Figure 3. The authors would like to thank Dr. Stephen Baylor for pointing out the error.
Both the HTML and PDF versions of the article have been corrected. These errors appear only in PDF versions downloaded on or before March 6, 2019.