THE BEGINNINGS OF LIFE. 39 



fact that even the most typical colloids are capable of 

 undergoing that kind of isomeric molecular change 

 which converts them into crystalloids. As one of the 

 best instances of this we may mention the fact of the 

 change which blood pigment undergoes. Haematoidin 

 is frequently met with in the form of oblique rhombic 

 crystals, and in addition there are other crystalline 

 forms of albumenoid substances obtainable from blood ^. 

 Amongst these may be included certain tetrahedral 

 crystals discovered by Reichert in connection with the 

 placenta of the guinea-pig, the behaviour of which to 

 reagents renders it certain that they were of an albu- 

 menoid or protein nature. Chlorophyll also has been 

 observed in a crystalline state by M. Trecul^, whilst 

 Dr. Montgomery '^ has depicted the results of a similar 

 change which a tube of myeline had undergone. 

 These facts sufficiently prove that no impassable bar- 

 rier exists between the crystalloid and the colloid 

 states of matter *. Do we not see that simple saline 



^ See an article on ' Albuminous Crystallisation ' in * Brit, and For. 

 Med. Chir. Rev.,' Oct. 1853. 



^ ' Comptes Rendus,' t. Ixi. p. 436. 



2 ' On the Formation of so-called Cells in Animal Bodies,' 1867. 



* In a paper recentfy read before the Royal Society (Proceedings, 

 vol. xix. [1871] p. 455), by Dr. Marcet, entitled, ' An Experimental 

 Inquiry into the Constitution of the Blood and the Nutrition of 

 Muscular Tissue,' he states, ' that a mixture of colloid phosphoric 

 anhydride and potash can be prepared artificially by the dialysis of a 

 solution of chloride of potassium and phosphate of sodium, and that 

 the colloid mass thus obtained appears to retain the characters of the 

 neutral tribasic phosphate.' Dr. Marcet finds, moreover, ' that blood 

 contains phosphoric anhydride and iron in a perfect colloid state, or 



