224 



CYTOLOGY 



levels to a visible cn'stalline pattern in 

 the cell units. Even before the basic 

 revelations of the X rays the geneticists 

 had established a definite linear pat- 

 tern of the particulate hereditar)' units, 

 or genes, in the chromosomes of the 

 germ cell nuclei. Apparcnth' the actual 

 gene particle is below the resolving 

 power of the electron microscope, 

 though some authorities are convinced 

 that in certain instances genes may 

 actuallv be seen. At all events, it is 

 definitely established that the genes in 

 a chromosome are arranged in a precise 

 pattern. 



Thus the present situation relative 

 to the structural pattern of protoplasm 

 may be summarized by saying that in 

 essentially all instances, where the new 

 methods have been used, evidence has 

 been obtained of an inherent cr\'stal- 

 line pattern just as is found in inorganic 

 solids. It therefore becomes evident 

 once more that the difference between 

 inorganic and organic substances lies 

 primarily in the much greater com- 

 plexity of the latter rather than in a 

 different method of construction. 

 Many major details of the cr\'Stalline 

 patterns of the varied lifcstuffs are still 

 undisclosed, but a firm foundation has 

 been laid, and the years ahead will 

 undoubtedly record substantial prog- 

 ress. 



MOLECULAR SIZE IN THE 

 PROTEINS AND VIRUSES 



The data accumulated has made it 

 possible to determine the molecular 

 weights and dimensions of a wide range 

 of proteins and viruses for comparison 

 with cellular units of living organisms. 

 The data on particle size may be ar- 

 ranged to show a gradual increase, be- 

 ginning with the smallest ultramicro- 

 scopic protein molecules and continu- 

 ing with the virus and bacteriophage 

 units up to the cell of the smallest 

 known bacterial organism and, finally. 



to cellular units of microscopic visibil- 

 ity. 



THE CELL AS A STRUCTURAL UNIT 



Turning our attention to the cell of 

 the biologist, it is important to inquire 

 whether the fullv established facts of 

 organic structure, as just outlined, give 

 any grounds for bringing cellular or- 

 ganization, which is almost universally 

 associated with the living organism, 

 into direct relationship with the struc- 

 tural patterns of the elemental ma- 

 terials from which it is built. In other 

 words, is the cell considered purely as 

 a structural unit an entirely distinct and 

 unrelated entity in the material world, 

 or does it represent the climax of a 

 gradually increasing complexity in pat- 

 tern having direct continuit\' with the 

 structural forms of less complexity as- 

 sociated with the materials of the non- 

 living world? May it not be possible 

 that the cell is essentially a protoplas- 

 mic CR'Stal in which an almost infinite 

 number of protein molecules, begin- 

 ning with the genes in the chromo- 

 somes, are associated in a specific ultra- 

 microscopic pattern characteristic of a 

 particular type of cell? In such a con- 

 dition independent protein molecules 

 are not present, but all are organized 

 to form the complete cell unit ex- 

 hibited in the crystalline pattern of a 

 specific t}pe of protoplasm. 



In a ver)' real sense, therefore, the 

 cell may be regarded as a molecule of 

 protoplasm; the least amount of this 

 lifestuff which will exhibit the charac- 

 teristics of the living state, just as a 

 single molecule of sugar or hemoglobin 

 is the indivisible unit of these sub- 

 stances. Tliis condition becomes par- 

 ticularly evident in the enormous 

 protein molecules of the virus and bac- 

 teriophage particles which have the 

 greatest molecular weight of any known 

 protein. 



There is a difference of opinion 



