6o Chemical Basis of Genus and Species 



Thrush, Emu, Greenfinch, and Hedge-sparrow egg-albu- 

 mins were tested and gave traces of precipita, as also did 

 Tortoise and Turtle sera. The egg-albumins of the Tor- 

 toise, Frog, Skate, and two species of Dogfish did not react. 

 Alligator, Frog, Amphiuma, and Dogfish sera also yielded 

 no results.' 



By improving the quantitative method in various 

 ways, Welsh and Chapman =" were able to explain why 

 the precipitin reaction with egg-white was not strictly 

 specific but gave also, though quantitatively weaker, 

 results with the egg-white of related birds. They 

 found that by a new method devised by them *'it is 

 possible to indicate in an avian egg-white antiserum 

 the presence of a general avian antisubstance (pre- 

 cipitin) together with the specific antisubstance." 



The Bordet reaction was not only useful in indicating 

 the specificity and blood relationship for animals but 

 also among plants. Thus Magnus and Friedenthal^ 

 were able to demonstrate with Bordet *s method the 

 relationship between yeast {Saccharomyces cerevisice) 

 and truffle (Tuber hrumale). 



5. We must not forget, while under the spell of 

 the problem of immunity, that we are interested at 

 the moment in the question of the nature of the speci- 

 ficity of living organisms. It is only logical to conclude 



* Nuttall, pp. 345 and 346. 



« Welsh, D. A., and Chapman, H. G., Jour. Hygiene, 1910, x., 177. 

 3 Magnus, W., and Friedenthal, H., Ber. d. deutsch. hot. Gesellsch.^ 

 1906, xxiv., 601. 



