THE PRECIPITINS AND THEIR ANTIBODIES 265 



favour of the view that all solutions of proteins may be 

 regarded as pseudo-solutions, i.e. consisting of suspensions 

 of finely divided particles. Against this view it may, how- 

 ever, be urged that the presence of some submicroscopic 

 particles does not prove at all that the whole of the quan- 

 tity of protein present, or even that a considerable part of 

 it, is in this state of pseudo-solution. 



Even in this case some salts, especially those of calcium, 

 strontium, and barium, exert a great influence, just as in 

 the case of agglutination, with which the phenomenon of 

 coagulation shows many analogies. (Cf. above, pp. 73 and 

 159.) Just as salts are of marked influence on the agglom- 

 eration of fine particles, as, e.g., of clay or of mastic (cf. p. 

 1 59), so in the same way the influence of the salts of Ca, 

 Sr, and Ba on the process of coagulation is so prominent 

 that it is doubtful if coagulation can be realised in their 

 absence. These salts alone, without rennet, give precipi- 

 tates with milk or solutions of casein. The coagulated 

 matter is more flocculent and does not entangle the fat- 

 drops to so high a degree as the coagulum produced under 

 the action of rennet. But this action of the salts of the 

 metals of the calcium group seems to be rather specific. 

 Next to them come the salts of magnesia, which accelerate 

 also the coagulation by rennet if they are present in greater 

 quantity, though according to Lorcher's observations small 

 quantities of MgCl 2 retard the action of rennet, whereas 

 even the least traces of Ca, Sr, or Ba salts accelerate the 

 coagulation by rennet. These salts give without ren- 

 net a coagulation with the casein of milk. Salts of the 

 other alkali metals coagulate milk only at high concentra- 

 tions ; they retard the coagulating action of rennet. In 



