154 MACROMOLECULAR COMPLEXES 



tiv'e and negative phases, indicating that the chemical changes 

 involved are so extensive that, according to Nachmansohn (1959): 

 "they ought to be susceptible to biochemical analysis" (p. 7). In 

 view of the characteristic coupling between the enzymatic reac- 

 tions and these ordered lamellar structures, a systematic investiga- 

 tion of excited nerve fibers by means of cryofixation techniques 

 might be rewarding. In this way, it may be possible to detect at 

 the molecular level the structural correlates of the role of the acetyl- 

 choline system in the permeability changes associated with nerve 

 conduction, as postulated by Nachmansohn ( 1959 ) on the basis of 

 his classic studies of the biochemical mechanisms of nerve activity. 

 Tissue culture techniques (Hild, 1957; Peterson and Murray, 1955) 

 should be of great operational value in connection with ultrarapid 

 freezing because of the critical limitations imposed by the specimen 

 size. Chemical and biochemical investigations (Folch et ah, 1958) 

 of the myelin sheath and other lamellar systems will continue to 

 provide the frame of reference for all research in this field, making 

 full use of the specific advantages inherent in the new techniques 

 for the study of enzymatic activity by electron microscopy ( Barrnett 

 and Palade, 1959), high-resolution autoradiography (Fernandez- 

 Moran, 1959d; Hoerlin and Hamm, 1953), and related cytochemical 

 methods. With an integrated physiological, biochemical, and bio- 

 physical approach, we may thus hope to gain a better understand- 

 ing of these Huid crystal elements which are the true "energy trans- 

 ducers of life." 



Summary 



A review is presented of the salient structural features of repre- 

 sentative lamellar systems in the nerve myelin sheath and in photo- 

 receptors, as revealed bv high-resolution electron microscopv, 

 using standard preparation techniques and improved low-tempera- 

 ture preparation methods based on rapid freezing with liquid helium 

 II. The information obtained by correlative application of direct 

 and indirect methods has furnished a reliable basis for evaluation 

 of the findings obtained with the new methods. Characteristic 

 paracrystalline granules of the retinal pigment epithelium in the 

 guinea pig are described. The molecular organization of lamellar 

 systems is discussed in relation to general concepts of energy trans- 

 fer processes which are emerging from recent biochemical and bio- 

 physical studies. 



