PART II 

 NERVE 



MORPHOLOGY IN MUSCLE AND NERVE PHYSIOLOGY 



by 



FRANCIS O. SCHMITT 



Department of Biology, Massachusetts Institute of Technology, 

 Cambridge, Mass. (U.S.A.) 



As applied to biology, morphology embraces the study of the structure of cell and 

 tissue constituents from gross and microscopic anatomy through the colloidal range and 

 even to the molecular and atomic levels. With the introduction of electron microscopy 

 it is now possible to visualize directly the structure of objects throughout the colloidal 

 range. It is not unrealistic to expect that technical development will make possible 

 direct visualization of such biologically important objects as the smaller protein mole- 

 cules and possibly even the polypeptide chains. Simultaneously the theory and tech- 

 niques of X-ray diffraction are also progressing. This method is already able to deal 

 effectively with the analysis of the internal architecture of certain crystalline proteins ; 

 a major hurdle appears to be the development of suitable computing methods — a 

 matter chiefly of technology and patience. Progress is also being made in the analysis 

 of the less regularly constructed, but no less important biologically, fibrous proteins and 

 complexes of proteins with lipids, nucleic acids and polysaccharides. This, too, is a 

 matter of painstaking, patient development of techniques, experimental and theoretical. 



Morphology is a science in its own right. The analysis of the detailed structure of 

 the molecules and complexes which occur in tissues is largely the task of the physicist 

 who, in turn, must depend upon the chemist to identify, isolate, purify and characterize 

 the individual constituents. In the normal course, as physicists and chemists become 

 interested in such substances, one may expect knowledge in this branch of crystallo- 

 graphy slowly to unfold. Slowly because such complex, frequently imperfectly structured 

 materials are not attractive to most crystallographers who are likely to regard them as 

 "sick crystals", as one colleague expresses it. Actually, some of the most important 

 protein crystals are far from "sick" structurally; upon the regularity of the internal 

 structure of their molecules depend such fundamental vital properties as are manifested 

 in the phenomena of immunology, genetics, and the ordered processes of growth and 

 development. Relatively minute changes in the structure of certain protein molecules 

 may make the organism sick (Pauling et al.^, recently referred to sickle cell anemia as 

 a "molecular disease" !). The great biological significance of structural studies has stimu- 

 lated many physicists and chemists to devote their efforts to the problem. Hopefully 

 their numbers will grow. 



The detailed analysis of biomolecular structure is a long term task. The analysis 

 starts with a rough characterization of the main structural features of a particular tissue 

 entity. With the aid of the electron microscope the biologist relatively untrained in the 

 discipline of crystallography can and must take an active in this phase. As the analysis 

 References p. 76}yy. 68 



