84 Intracellular Proteins [Sept. 



the time when the relation between colloid and crystalloid may be 

 viewed as merely a matter of size of molecules. Adsorption is a 

 new term to meet this condition of salt and protein combination 

 and may clear up some of our problems by showing the significance 

 of adsorptive affinity as distinct from ordinary chemical affinity. 



Compounds of proteins. Many so-called protein salts have 

 been made in the laboratory. Many have been produced in our own 

 laboratory. They show properties which would lead us to consider 

 them ordinary chemical Compounds, in some cases, and adsorption 

 products in others. Dyes, too, seem to enter into definite chemical 

 combination with proteins. 



In general, then, I have tried to show that on all the points of 

 special interest as regards cell proteins the State of our knowledge 

 is extremely meagre, but that already much has been done and that 

 there is great opportunity for the biochemical study of proteins to 

 aid materially every other brauch of biology. That it already has 

 helped is shown in its contributions to the study of problems like 

 fertilization, dietetics, protein metabolism and its relation to disease. 



VI. INTRACELLULAR EXTRACTIVES 

 Isidor Greenwald 



The term " extractives " is generally applied for convenience 

 to all the organic constituents of cells and tissues which occur in 

 minute proportions and which cannot be classified under any of the 

 other subdivisions of to-night's program. Included among the ex- 

 tractives are substances of the greatest diversity. Some of them, 

 such as Urea, are end-products of metabolism, while others, such as 

 creatin, may be of great functional significance in cells. 



Because the extractives occur only in small proportions, inves- 

 tigation of their significance is very difiicult. Of all the sources 

 of supply, the commercial extract of beef is the most con- 

 venient. Consequently the extractives obtained from it have been 

 studied most carefully. Then too, muscle contains more extractive 

 substance than does any other tissue. Moreover, the extractives of 

 other tissues are qualitatively similar to those of muscle, though 

 quantitatively much difference exists. For this reason these re- 

 marks are confined almost entirely to the muscle extractives. 



