408 Co7iclusions 



The precipitins and precipitable substances combine quantitatively. 

 The precipitum is soluble in an excess of precipitable substance. 

 Heated antisera cannot be reactivated. The precipitins constitute 

 receptors of the second order (Ehrlich). There is no evidence that the 

 action of precipitins is fermentative. Heated haematoserum (precipitoid) 

 combines with precipitin, and prevents its action upon precipitable 

 substance. There is evidence of the existence of immune-bodies in 

 precipitating antisera. There is no evidence that antisera differ in 

 their ordinary properties from normal sera. The precipitins and pre- 

 cipitable substances are intimately bound up with the globulins in 

 serum, and have not been separated therefrom. The precipitins do not 

 give reactions corresponding to the amount of albumin present in a 

 solution of precipitable substance ; the albumin, to be acted upon, must 

 possess certain specific properties. The presence of even small quantities 

 of acids or alkalis, markedly reduces the amount of precipitum formed, 

 but an increase of salt (NaCl) has little effect. The supernatant fluid 

 in a mixture of antiserum and precipitable substance, after precipitation 

 has taken place, may contain an excess of both interacting bodies. 

 There is evidence that the precipitins may exert a special, but not a 

 specific action on different albumins from the same species of animal. 

 It is doubtful if the precipitins and precipitable substance can withstand 

 tryptic digestion, whereas both are certainly destroyed by peptic 

 digestion. The weight of evidence is against the possibility of preci- 

 pitins being formed for peptones \ 



The rate at which interaction takes place between precipitins and 

 precipitable bodies is markedly influenced by temperature, being re- 

 tarded at low temperatures, hastened at higher temperatures. The 

 quantity of precipitum formed is not influenced by the temperature 

 (5 — 37° C.) at which the experiment is made. Undiluted haematosera 

 are but slightly affected by exposure to a temperature of 63° C, ; they 

 are inactivated at 68 — 70°, unaffected at 60° and under. (Bacterio- 

 precipitins are inactivated at 58 — 60° C.) Undiluted normal sera seem 

 to be rendered non-precipitable at a somewhat lower temperature than 

 that which inactivates haematosera. Both interacting bodies resist 

 desiccation. The precipitins are apparently more unstable than the 

 precipitable substances, which may give reactions even when dried 

 many years. Fluid sera, preserved in vitro, may give reactions after 

 being stored 4 or more years ; they appear to deteriorate slightly by 



' See Appendix, note 2. 



