PROTEINS 497 



of the lake lamprey when mixed with the blood of a bony fish, 

 such as the lamprey often feeds upon, prevents the coagulation 

 of the blood. The secretion is effective in preventing or delaying 

 the coagulation of human blood when the two are artificially 

 mixed. 



Anesthesia. — Some sixty years ago, Claude Bernard advanced 

 the hypothesis that anesthesia involves the reversible coagulation 

 of the colloids of the sensory nerves by the anesthetic. The 

 hypothesis was rejected because it was (until quite recently) 

 thought that a coagulum is incompatible with life. This criticism 

 has been met by showing that the amount of anesthetic (alcohol) 

 necessary to coagulate a colloid may be quite small and that 

 under these conditions the coagulation is reversible. The theory 

 of Bernard has been revived and given newer support by Ban- 

 croft. That we lose consciousness under an anesthetic because 

 the protoplasm of our nervous system is coagulated, mildly and 

 reversibly, is a plausible hypothesis. Severe, irreversible 

 coagulation means death. 



There are numerous other hypotheses of anesthesia none of 

 which is fully accepted. 



Cellular Agglutination. — Bacteria in culture are often to be 

 seen clumped together in isolated groups. They have agglu- 

 tinated. This means death unless they are soon redispersed. 

 The cause of bacterial agglutination is a reduction in their surface 

 potential, not charge (see page 372) — at least so it would seem from 

 the work of Northrop and Kunitz, who have shown that certain 

 bacteria agglutinate at a definite minimum electric potential of 

 11 mv. (page 376). The relationship between potential and 

 agglutination is specific and not general; that is to say, each 

 species has, within limits, its own particular minimum potential 

 at which it agglutinates. 



The agglutination of bacteria plays a significant part in the 

 defense mechanism against disease. It is not in itself sufficient 

 to render pathogenic bacteria inert, for the attack on bacteria 

 within the body is one of chemical neutralization (page 502) ; 

 that is to say, antitoxins function through chemical union with 

 toxin, but agglutination is usually associated with chemical 

 neutralization and thus may contribute. 



There is a very remarkable type of cellular agglutination 

 which does not belong strictly to the purely physicochemical 



