Some inquiry has been received by the State Board of Horse Commissioners relative to the capsule method of breeding mare. With the thought that a brief statement of the instruments used and the methods employed in the so-called capsule method of breeding might be useful to stallion men in general, this little circular has been prepared.
Carroll, W. E. and Frederick, J., "Circular No. 20 - Capsule Method of Breeding Mares" (1916). UAES Circulars. Paper 16.