658 Transactions of the Society. 



momentary precipitation of albuminate is followed by solution in 

 excess of acid. Then the small molecules disappear to a large 

 extent. But the larger remain, and are motionless. 



If, again, a solution of acid-albumen be prepared in any way 

 (as by warming fresh albumen with dilute hydrochloric acid, or 

 by digesting dried albumen or dried alkali -albumen with dilute 

 hydrochloric acid) and be well shaken with an equal bulk of oil, an 

 emulsion is formed, but with difficulty, and with no approach to the 

 completeness of the alkaline emulsion. 



The particles of this emulsion manifest tolerably active and 

 persistent movement. But the addition of strong hydrochloric acid, 

 which is in this case not attended with any precipitation of albumen, 

 almost entirely stays all movement, in many cases arrests it com- 

 pletely. In this respect my experience is the same as that of Professor 

 Jevons, who finds that molecular movement is hindered by acids. 



Such emulsions left in test-tubes for some time show very 

 interesting microscopical phenomena. An alkaUne emulsion, made 

 with neat's-foot oil, examined at the end of sixteen days, had a 

 thick, white cream on the surface, the fluid beneath remaining of a 

 pale, thin sky-blue. 



The cream consisted of a mixture of minute and most vivacious 

 molecules with larger spherules — as much as xuVt7 or ^^^ inch in 

 diameter. They had thick walls, often sharply laminated, and 

 contained either clear fluid, or one or more oil-globules floating in 

 clear fluid, or a dense cloud of vibrating molecules of the smallest 

 size, or, lastly, smaller vesicles enclosing globules or molecules piU- 

 box-fashion. The conditions here at work were, apparently, 1st, 

 an expansion of the haptogen membrane of spherical globules by 

 osmose ; 2nd, a continuous addition to the surface of the membrane ; 

 3rd, a repetition of the original membrane-forming action, following 

 the contact of ingoing soluble alkali-albumen with the contained oil, 

 or solution of the oil by the alkali. In the acid-albumen (syntonin) 

 emulsion the smallest molecules had mostly disappeared by the end 

 of sixteen days ; the general movements were sluggish and shght. 

 Laminated vesicles of large size abounded (see Figs. 1 and 2). 



Comparing these emulsion experiments with those observations 

 in which particles of gamboge, Indian ink, or china-clay, are sus- 

 pended in a chemically indifferent fluid, such as pure water, the 

 introduction of at least two new sources of movement may be con- 

 tended for. 1st, the chemical surface tension already noticed ; 

 2nd, vibrations or intestinal disturbances in the colloid suspend- 

 ing fluid, such as attend its decomposition, or its metamorphosis, 

 or its resolution into a crystalloid. 



As regards the first, the formation of an emulsion is most per- 

 fect, and the movements of molecules are most active, when the 

 chemical action between the oil and the albuminous solution is 

 most active. The acid-albumen, the simple egg-albumen, and the 



