The Collaborative International Dictionary of English v.0.48:

Proteid \Pro"te*id\, n. [Gr. prw^tos first.] (Physiol. Chem.)
   An older, imprecise term replaced by protein.

   Note: Proteid was defined in the 1913 Webster as "One of a
         class of amorphous nitrogenous principles, containing,
         as a rule, a small amount of sulphur; an albuminoid, as
         blood fibrin, casein of milk, etc. Proteids are present
         in nearly all animal fluids and make up the greater
         part of animal tissues and organs. They are also
         important constituents of vegetable tissues. See 2d
         Note under Food." -- Pro"te*id, a.

   Syn: protein.
        [1913 Webster +PJC]

   Defensive proteid (Physiol. Chem.), one of a class of
      proteid substances, present in some animal tissues and
      fluids, that make the body immune to certain infectious
      diseases by destroying or rendering inactive the toxic
      products of bacterial growth; -- this is an older term
      replaced by more precise modern immunological concepts
      such as antibody and immunoglobulin. [archaic]
      [Webster 1913 Suppl. +PJC]