LYSINS 155 
precipitins, and biological relationships have been established, based 
upon the comnuniity of these antibodies. Thus, the sera of certain 
anthropoid apes^ are said to be precipitated by the sera of animals 
immunized to the serum of man; sera from the lower monkeys fail to 
react with the human serum. From these observations the inference 
has been drawn that these anthropoid apes are more closely related to 
man than are the lower monkeys.- 
Precipitins closely resemble agglutinins in their method of forma- 
tion, their resistance to physical agents and their reactions. Like 
the agglutinins, they possess both a thermostabile haptophore or 
combining group and a thermolabile ergophore group. The precipi- 
tinophore group is very labile and readily becomes non-functionating, 
but the combining group is relatively stabile. A precipitin which 
has lost its ergophore group is called a precipitinoid according to 
Ehrlich's nomenclature. It seems rather more probable that the inhi- 
bition is due to excess of antigen as Opie showed. (See page 154.) 
The precipitate formed by a specific serum acting upon a clear 
solution of the antigen {precipitinogen) probably is derived from the 
serum, because very dilute solutions of the immunizing protein will 
throw down a relatively bulky precipitate, far too great in amount 
to come from the antigen in the dilution used.^ 
Precipitins have been extensively studied in their relation to cer- 
tain aspects of forensic medicine, but they have little practical value 
in the laboratory diagnosis of bacterial disease. They are found in 
sera under the same conditions as agglutinins, but the technique for 
their demonstration is more involved than that for agglutinins. Their 
relation to immunity is unknown, but probably similar to that of 
agglutinins. The observations of Weil,* however, are of significance. 
He was able to passively sensitize guinea-pigs by injecting them with 
the precipitate formed by the interaction of an antiserum and its 
antigen. 
LYSINS. 
Mention has been made (see preceding section) of the bactericidal 
power of fresh blood serum of a normal animal and man. This 
important discovery, that normal sera contain substances that will 
destroy moderate numbers of bacteria, was made by Nuttall," who 
also obser\'ed that there was a limit to this destructive activity and 
that this property was lost upon standing, or rapidly destroyed by 
an exposure of the serum to 55° C. for one-half hour. Buchner'^ cor- 
roborated and extended these observations and designated the unknoA\Ti 
1 Grunbaum: Lancet, 1902, i, 143. 
2 See Nuttall (Jour. Hyg., 1901, 1, 367; Proc. Roy. Soc, November, 1901, 69, 150; 
British Med. Jour., 1902, i, 825) for full details. 
' Welsh and Chapman: Ztschr. f. Immunitiitsforsch., orig., 1911, 9, 517; British 
Med. Jour., 1910, ii, 1510. 
* Jour. Immunol., 1916, 1, 19. s Ztschr. f. Hyg., 1888, 4, 353. 
« Centralbl. f. Bakteriol., 1889, 5, 817; 6, 1, 561. 
