336 Dr Nuttall, Further Observations on Blood. 



tions of Alligator sinensis and Testudo ibera, a faint clouding with 

 A. mississippiensis and Ghelone midas. This anti-serum produced 

 no clouding in mammalian or other bloods. Should further in- 

 vestigations show similar reactions with other reptilian bloods, 

 then we may perhaps be able to assume that the egg still possesses 

 a vestige of reptilian character. It is however too early to draw 

 any conclusions. 



Anti-alligator serum, prepared by injecting rabbits with the 

 serum of A. mississippiensis, produced a reaction on being added 

 to serum dilutions from A. mississippiensis and A. sinensis, a faint 

 clouding in the blood of Ghelone midas. 



Anti-turtle serum (from Ghelone midas) acted upon turtle blood, 

 but in addition produced a marked clouding in the blood of Testudo 

 ibera, a very faint clouding with A. mississippiensis, no other bloods 

 being affected. 



Anti-lobster serum (from Homarus vulgaris) reacted with 

 lobster serum dilutions, produced marked clouding with blood 

 of Astacus Jluviatilis, but exerted no effect whatever on any of the 

 250 bloods examined, as in the preceding cases 1 . 



I come finally to the consideration of the reaction which takes 

 place in non-homologous or distantly related bloods when these 

 are allowed to stand. From the first, I found it necessary, in 

 making these tests, to put a time limit upon them. This may 

 appear to be a rather arbitrary proceeding. My time limit has 

 usually been five minutes at average temperatures in the laboratory. 

 A powerful anti-serum will certainly have acted within that time 

 upon its homologous blood-dilution ; with powerful fresh anti-sera 

 the reaction takes place almost instantaneously. On the other 

 hand, if we allow the mixtures of anti-sera and bloods to stand, 

 a reaction takes place slowly with non-homologous bloods. The 

 results I have hitherto obtained tend however to prove that anti- 

 mammalian sera only produce these later reactions in mammalian 

 bloods, and anti-avian sera act similarly on avian sera alone. 

 I am at present engaged in carefully observing these slower 

 reactions. The results above recorded are based upon observations 

 made within the arbitrary time limit. 



1 Note whilst going through the press : — I have since found that anti-lobster 

 serum produced slight reactions or marked clouding with blood dilutions of five 

 species of crab, viz. Portuntis depurator, P. puber, Carcinus maenas, Cancer pagurus, 

 Eupagurus bernhardus. 



