In the theory of electrocardiography the direction of myocardial fibers has been almost ignored. In order to evaluate whether this is proper or not, directional difference of conduction velocity in the ventricular syncytium was examined by capillary microelectrodes. Conduction velocity in the direction of myocardial fibers was found to be usually several times larger than that vertical to them. This difference is significantly large and cannot be ignored even though rapidity of conduction through Purkinje fibers is considered. This statement became more applicable in various abnormal conditions. Thus it is concluded that the direction of myocardial fibers should be given more attention in discussion of propagation of excitation waves in the cardiac ventricle.
STIMULATION of various parts of the rhinencephalon is known to produce seizure-like electrical after-discharges in the cerebral cortex. Kaada1 has recently explored this subject at length and reviewed the pertinent literature. In recent studies 2 it has been shown that stimulation of the dorsal fornix and the fimbria hippocampi in the guinea pig and cat leads to cerebral and cerebellar afterdischarges. Although they appear to spread over neural pathways and can be induced by stimulation of the fibers of the fimbria alone,2c the precise routes involved are not yet clear, and the possible role of volume conduction in their propagation is not yet settled. The participation of subcortical structures, as well as their importance in the maintenance of the after-discharges, is also a matter requiring further study. Finally, the effects of stimulation of the fimbria in unanesthetized and unparalyzed animals is of interest, for, although Penfield and Erickson 3 found that stimulation of the hippocampus produced no motor response in humans, recent studies by Kaada and Jasper 4 indicated that a grand-mal type of seizures could be induced, and Hunter ' observed petit-mal-like effects in conscious cats when the general region of the fornix was stimulated. This study is an attempt to eluci¬ date these problems.
The introduction of the scanning electron microscope into biological research has revolutionized the possibilities of studying the surface structures of biological specimens. The method was used originally for the surface of hard tissue ; however, the improved fixation method, which preserves quite well the ultrastructure of soft tissues as shown by Barber and Boyde (1968) ,1) has now made it possible to observe the fine structure of the surface of soft tissues.The present investigation is a study of the surface of vascular endothelium in the rabbit and man. These endothelia have already been studied by transmission electron microscopy, so their structure is partially known. This is the preliminary report of the study.
Materials and methods.The endothelial surface of aortas, coronary and renal arteries, inferior vena cavas, right and left ventricles and atria from 13 male rabbits and aortas, inferior vena cavas, right and left ventricles and atria of two men, 21 and 74 years old, who died of Crohn's disease and myeloma, respectively, were examined in the present study.The method of Barber and Boyde (1968)1) was modified and used. Namely, the isolated specimens were carefully washed by LockeRinger's solution, then 1 % osmium tetroxide (with veronal acetate to pH 7.4) was poured into the vessel lumen. The specimen was cut into small blocks 3 mm x 10 mm in size. The blocks were fixed for one hour under cold temperature in an ice-box and were dehydrated in graded Analar acetone solutions of 50%, 70%, 80%, 90%, 95%, and two changes of absolute acetone.After air drying, the specimens were mounted at an angle of 45° to an evaporation source and rotated during the deposition of a conducting coat of about 100300 A of gold in a vacuum.The specimens were studied with a scanning electron microscope (JSM-II) of Japan Electron Optics Laboratory Co. Ltd., using a beam accelerating voltage of 610 0 Ky. The micrograph recorded with a scanning electron beam on the film with an exposure time of 3060 seconds.
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