252 Dr. A. Macfadyen, Dr. G. H. Morris, and Mr. S. Rowland. 



together with a proportion of added silver sand, in a condition of 

 violent agitation, in such a manner that in the rapidly succeeding 

 mutual impacts of yeast-cell and sand-particle the cell wall is ruptured 

 and the contents expelled.* 



If the dry mass of yeast and sand be watched while disintegrating 

 it will be seen to become rapidly pasty, and through successive stages 

 of viscidity it finally reaches a perfectly fluid condition. A micro- 

 scopical examination at the end of the process fails to discover any 

 whole cells. During the continuance of this process, and in fact 

 during the whole time that elapses between the rupture of the first 

 cell wall and the examination of the final product, the material is kept 

 cool by means of a brine circulation. The brine is maintained at a 

 temperature of - 5 C. by means of expanding anhydrous ammonia. 

 This suffices to keep the disintegrating mass at about 15 C. If this 

 precaution is not adopted the temperature will rise to nearly boiling 

 point, owing to the mechanical production of heat by the impacts and 

 friction of the disintegrating mass. 



It now remains to separate the escaped intracellular juices from the 

 suspended cell walls. This is accomplished by a repetition of the 

 same process by which the adherent water was removed from the 

 original yeast. To reduce the mass to a consistency capable of being 

 dealt with by the press, kieselguhr is added (Buchner uses this sub- 

 stance together with sand for grinding). The addition of this substance 

 also serves as a filtering material, and allows the expression from the 

 doughy mass as from a sponge of a perfectly clear opalescent pro- 

 duct in which no suspended particles can be discovered. A pressure 

 of from 200 300 atmospheres is requisite to express the contained 

 fluid. Such are the main outlines of the method which has been 

 adopted in the preparation of the juice on which the observations that 

 follow were made. 



It may be useful to give figures representing the method as it 

 operates in practice on an averagely successful preparation. 



From 100 grammes of dried and pressed yeast will be obtained 

 from 30 35 c.c. of expressed juice. The weight of sand employed 

 for grinding will be 100 grammes, and the weight of kieselguhr 

 necessary to reduce the ground mass to a suitable consistency for 

 pressing will be about 80 grammes. The specific gravity is usually 

 from 1050 1060, and the time necessary to completely disintegrate 

 the above quantity of dried yeast is usually 3\ hours. 



The physical properties of the juice correspond closely with those 

 described as characteristic by Buchner. The contained proteolytic 



* The precise details of this process, which has been successfully employed for 

 the disintegration of micro-organisms, internal organs, glands and muscle fibres, 

 will form the subject of a separate paper. 



