[21]. Opie, Freeman, Blake, Small, and Rivers: Jour. Am. Med. Assn., 1919, lxxii, 108.
[22]. Vaughn and Palmer: Jour. Lab. and Clin. Med., 1918, iii, 635.
[23]. Soper: Jour. Am. Med. Assn., 1918, lxxi, 1899.
[24]. Cole and MacCallum: Jour. Am. Med. Assn., 1918, lxx, 1146.
[25]. Hammond, Rolland, and Shore: Lancet, London, 1917, ii, 41.
[26]. Abrahams, Hallows, Eyre, and French: Lancet, London, 1917, ii, 377.
[27]. Public Health Reports, U.S.P.H. Service, 1919, xxxiv, 33.
[28]. Blake: Jour. Exper. Med., 1917, xxvi, 67.
[29]. Avery: Jour. Am. Med. Assn., 1918, lxx, 17.
[30]. Dunn: Jour. Am. Med. Assn., 1918, lxxi, 2128.