38 The Structure of Protoplasm 



by denaturation. Indeed this may be the case with the proteins in- 

 vestigated by Banga and Szent-Gyorgyi. Perhaps these intrapro- 

 toplasmic structural proteins should be classified as a separate group. 

 At all events, it appears evident that many of the physical prop- 

 erties of protoplasm can be ascribed to its proteins and that these 

 provide a labile, structural framework within which metabolism 

 can take place. It has been suggested that the cell is a "protein 

 crystal." Although varying portions of the cell may exhibit transi- 

 tory birefringence, the notion of a whole cell as a crystal seems too 

 static. To use the words of Frey-Wyssling (13), "Das Haftpunkt- 

 system der lebenden Substanz ist daher nicht etwas Oegebenes, wie 

 z. B. bei Gelatine- oder gar bei Zellulosegelen, sondern bestandig ist 

 bei ihm nur der Wechsel!" 



FOOTNOTES 



'For a discussion of theoretical aspects of polarization microscopy, see 

 Ambronn and Frey (2), Schmidt (41), and Schmitt (42). 



'It is suggestive that Coult (8) has found that germination of seeds is accel- 

 erated by shaking them. Shaken seedlings showed a significantly greater increase 

 in weight (wet and dry) over controls. 



■The results of Beams and King (5) are interesting in this connection. They 

 found that fertilized Ascaris eggs retained their capacity to cleave, even after 

 long centrifugation at 100,000 to 400,000 times gravity. Some eggs divided in the 

 centrifuge. These centrifugal forces are more than enough to sediment srnall 

 corpuscular proteins. Beams and King conclude that Svedberg's stratification 

 does not take place and that either there is no need for definite spatial relation- 

 ships or else the protoplasm does not behave as a free dispersion of protein 

 particles. The latter hypothesis seems more likely in the light of Mirsky's evi- 

 dence for a structural framework after fertilization. 



' Since the preparation of this chapter, Dr. Mirksy has brought the interesting 

 work of Bensley to my attention (Bensley, R. R., and Hoerr, N. L., Anat. Rec. 

 60:251-266. 1934; Bensley, R. R., Anat. Rec. 72:351-369. 1938). Bensley has 

 isolated structural proteins from the cytoplasm of liver cells in what appears 

 to be an undenatured state. The original articles should be consulted for 

 further details. 



BIBLIOGRAPHY 



1. Abramson, H. a., Gorin, M. H., and Moyer, L. S. The polar groups of protein 



and amino acid surfaces in liquids. Chem. Rev. 24: 345-366. 1939. 



2. Ambronn, H., and Frey, A. Das Polarisationsmikroskop. Leipzig. 1926. 



3 AsTBURY, W. T. X-ray studies of the structures of compounds of biological 

 interest. Ann. Rev. Biochem. 8:113-132. 1939. 



4. Banga, I., and Szent-Gyorgyi, A. Structure-Proteins. Science 92:514-515. 



1940. 



5. Beams, A. W., and King, R. L. Survival of Ascaris eggs after centrifuging. 



Science 84:138. 1936. 



6. Bull, H. B. Protein denaturation. Cold Spring Harbor Symposia on Quanti- 



tative Biology 6:141-149. 1938. 



7. Chambers, R. The physical structure of protoplasm as determined by 



microdissection and injection. In Cowdry, E. V. General Cytology, pp. 

 237-309. 1924. 



