June 27, 1919] 



SCIENCE 



601 



cept in the highly hydrated state known as 

 peptones, or when broken apart into compara- 

 tively simple amino-compounds. Gelatine, a 

 substance of an albuminous character, has 

 been widely used in experimental work which 

 had for its purpose the determination of the 

 properties of living matter, but we are now 

 so far advanced as to know that it may repre- 

 sent the qualities of the protoplast only in so 

 far as these may be identical with amphoteric 

 compounds. In other words, the behavior of 

 gelatine may be used to some extent to sim- 

 ulate the reactions of protoplasm which con- 

 sists largely of albuminous substances. This 

 is not a universal condition and in fact is the 

 ejcception in plants. 



Lipins or fatty substances form an im- 

 portant part of the living matter of animals 

 and in their growing cells may constitute as 

 niuch as two per cent, of the solid matter, 

 amounting to one part in a thousand of the 

 total weight. The lipins may unite with 

 phosphoric acid, with carbohydrates, or with 

 nitrogenous substances such as the amino- 

 acids; giving diverse materials, the action of 

 which in the life processes is but dimly com- 

 prehended. 



The physiologist who devotes himself to the 

 study of life as exemplified by animal forms 

 deals with a protoplasm in which the proteins 

 and lipins predominate, and is excusably apt 

 to believe in the universality of the properties 

 he uncovers by a study of their reactions. 

 The presence of mucin, gums and mucilages 

 in living matter has long been known, but the 

 determination of their definite occurrence as a 

 component part of the mechanism of the cell 

 was first acomplished at the Desert Labora- 

 tory. Numerous analyses show that the pen- 

 toses and their condensation products the pen- 

 tosans are abundant in plant cells, and that 

 they may form a larger proportion of its dry 

 weight than do the proteins or nitrogenous 

 substances. 



Here however, we must avoid the mistakes 

 of our predecessors by assuming a universal 

 condition. Specialized organs or cells, eggs, 

 spores, pollen cells, etc., may have a proto- 

 plasm in which the protein material may 

 make up almost the entire solid matter, and 



at the same time it is not to be assumed 

 that the main components are evenly distri- 

 buted throughout the mass of the protoplast, 

 as it is very well knovm that the nucleus and 

 other special organs of the cell are high in 

 albumins. Consultation of available informa- 

 tion on this point shows that in bacteria for 

 example over 90 per cent, of the solid matter 

 may be albuminous. The analyses of cacti 

 made by Dr. H. A. Spoehr at the Desert Lab- 

 oratory show that not more than a tenth of 

 the living matter is proteinaceous, and that 

 the greater part of the cell content is car- 

 bohydrate, pentosans, of which gum arable, 

 tragacanth, mucilage and agar are common 

 examples, these being in fact combinations of 

 the simpler pentose and hexose sugars. 



Miss Stewart of Barnard College has re- 

 cently described the manner in which pento- 

 sans formed in the cytoplasm accumulate in a 

 layer next the wall leading some observers to 

 believe mistakenly that they were formd by the 

 hydrolysis of wall material. In other cases 

 masses were formed in cavities in the proto- 

 plasm. Gross chemical analyses determine the 

 presence of such substances in material in 

 which they occur only in finely divided form 

 in the colloidal mixture and may not be de- 

 tected by microchemical methods. At present 

 our knowledge of these substances is confined 

 chiefly to their action as a part of the hydra- 

 tion or growth mechanism, and it is by no 

 means clear that they are not more or less 

 included in the metabolic cycle. 



These statements are not to be taken as im- 

 plying a simple composition for protoplasm: 

 The different and various pentosans on the one 

 hand and the amino-compounds built up by 

 the plant or derived from albimiins have va- 

 rious si>ecial characters although the first 

 agree in being weak acids, and the second are 

 amphoteric, capable of acting as either acids 

 or bases according to conditions. As an ex- 

 ample of these differences there has been much 

 discussion as to whether or not protoplasm 

 was soluble or miscible in water. It is ob- 

 vious that living matter in which the pentosan 

 was a mucilage like gum arable would be 

 miscible with water, while a pentosan like 



