Along the raphe of the brain stem, a series of small neuronal groups can be observed in the medulla oblongata, the pons and the mesencephalon. The neurons located in and adjacent to the raphe are considered to produce mainly serotonin (5-HT). The groups of nuclei containing 5-HT were first reported in experimental animals in the early 1960s. The presence of such nuclei, however, has not yet been brought to light in the human brainstem except the few atlases, although in several neuroanatomy textbooks, extrapolated data are shown in the form of drawings as if they were the data from the human brain. The aim of this study is to present microscopic photos of such raphe nuclei made from serial sections of the human brainstem, and to clarify the differences between findings in human and textbook drawings from animal data.

Morphological findings or evaluations of the nervous system have traditionally concentrated on cell somata; evaluations of the white matter have not been put forward up to now. This study was conducted to evaluate the white matter in the spinal cord with the LPH discriminative staining method which was proposed by Goto. Thanks to the minimum shrinkage ratio (10 ± 0% in length) which this technique allows, it is possible to evaluate the sizes of nerve axons, and to compare the arrangement of nerve fibers in various parts of the spinal white matter. As the axonal sizes reflect nerve conduction velocities, we would like to emphasize that these sizes or the differences in the arrangement of axons may be important for a better understanding of neurosymptomatology.

Using an ideal tissue preparation method, we found a definite correlation between various human neuronal somata from the view point of accurate morphometry and functional evaluations. We believe this study may be of value, or even indispensable in the correct understanding of neurological symptomatology and phenomenology.

It is generally accepted that nerve fiber conduction velocity is directly proportional to the fiber diameter under the condition, based on a supposition, that the transverse area of axons is normally maintained constant. Using an ideal preparation method for the purpose of axonal discrimination, we examined 43 human spinal cords after making transverse sections at the cervical, thoracic, lumbar and sacral levels and found a tapering of the axons in the lateral pyramidal tract, as the cross-sectional area of the pyramidal axons showed a definite decrease from the cervical to the sacral levels. Our results contradict the supposition that the transverse area of axons is normally maintained constant, which has for a long time been believed to be true without any evidence for it.

We carried out a morphometric comparison of tissue sections from the human spinal cord, medulla oblongata, cranial nerves, autonomic nerves and spinal nerves with the help of a very accurate method that includes two-step fixation, nitrocellulose embedding and discriminative staining. We conducted morphometric evaluations to compare various axonal areas between different individuals using a combination of an image analyzer and a high power microscope. Our study showed a negative correlation between age and axonal area in all nerves except the greater splanchnic nerve. We believe that such data would not have been discovered without the use of our sophisticated electronic equipment together with the special preparation method we employed. Recourse to such methodology will allow more precise study of neurohistology and lead to better understanding of the aging process in human beings.

We have conducted a study to compare various preparation methods, including a certain number of new methods, to find which ones are best suited to the morphological evaluation of nerve fibers in the pyramidal tract of the human medulla oblongata. Our main concern was to find fixation and staining methods that would minimize errors, especially regarding the tissue shrinkage ratio and the ease of staining. From the two fixation methods we examined, the most satisfactory was the secondary chromic acid fixation (which gave the best overall results when followed by nitrocellulose embedding), as it gives the lowest shrinkage ratio with the narrowest range (10 +/- 0%). Among the ten staining methods we tested, we found that the most suitable for morphological evaluation were the discriminative staining methods (Luxol fast blue-Periodic acid-Schiff-Hematoxylin stain, Masson-Goldner-Goto method and modified Hematoxylin-Eosin stain) and the silver impregnation methods (Luxol fast blue-Silver impregnation and Luxol fast blue-Silver impregnation-Periodic acid-Schiff-Hematoxylin).

Using a preparation method composed of secondary chromic acid fixation, nitrocellulose embedding and Luxol fast blue-PAS-hematoxylin stain (a discriminative staining method) for the purpose of axonal discrimination, we examined 43 human spinal cords (31 males and 12 females) at the C5 level to find the differences due to gender and aging in axons of the lateral corticospinal tract. These results can be of great help in understanding the motor functions in relation to gender differences and the aging process.

The aim of the present study is to analyze and compare nerve fibers of the human greater and lesser splanchnic nerves in relation to the aging process. The analysis was conducted with the use of a new fixation, embedding and staining method that makes it possible to discriminate various structures of the nervous tissue and with the help of an image analyzer. We examined 25 greater splanchnic and 30 lesser splanchnic nerves which were taken from cadavers (44–96 years) for anatomy dissection. The results showed that there was a decrease in transverse area and perimeter of axons in relation to aging process for the lesser splanchnic nerve, while there was an increase for the greater splanchnic nerve. This discrepancy may indicate a difference in sympathetic nerve controls between the kidney and abdominal organs during the aging process.

It is very important to evaluate and accurately understand the various conditions of the human nervous system. In this review article, we introduce several morphometric reports that are proven to be accurate from the view point of various errors (range of tissue shrinkage ratios, microscopic multiple counting, artifacts of microscopic structures, etc.). We review the following aspects of the selected reports: methodology, developmental research, neuronal differences, gender differences, aging process and miscellaneous (nerve fibers, unmyelinated fibers, in relation to neuropathology, clinical image-analysis and immunohistochemistry).

Using serial sections of 11 human brains of fetuses 18-40 weeks of gestation (WG), 2-month-old infant and 63-year-old adult, we conducted the quantitative analysis of the development of the posterior funicular nucleus (PFN) in the medulla oblongata. The results suggest the following: (1) The cells of the human cuneatus lateralis nucleus are easily distinguished from those of the gracilis nucleus and cuneatus medialis nucleus because the neuronal somatic areas are the largest; the smallest neuronal areas are in the cuneatus medialis nucleus. (2) The development of the PFN occurs at least in four stages characterized by the degree of maturation of the neurons: (a) immature neuronal stage before 20 WG, (b) preparatory stage between (a) and (c), (c) accelerated development stage from 30 to 40 WG, and (d) postnatal stage. The development of the human posterior funicular nucleus accelerates after 30 WG, and postnatal qualitative maturation also occurs. Developmental differences of the three nuclei of the PFN in the medulla oblongata are presented and discussed from the morphological and morphometric point of view.

We calculated numbers and axonal areas of myelinated nerve fibers in the Lissauer tract of the human lumbar spinal cord (L1) from the viewpoint of the aging process. We examined 20 human spinal cords from 13 males and 7 females, age ranging from 41 to 88 years old. We found that, although the number of nerve fibers showed no significant change in relation to the age of the subject, the axonal area of myelinated nerve fiber in the Lissauer tract did decrease with age.

We compared morphometric data on various nerve cells in the human special sensory system using the modified Klüver-Barrera staining method with an extremely minimized shrinkage ratio and an image-analyzer. According to the measurement data of cell-body sizes, we classified nerve cells of the various nerve nuclei in the special sensory system into three groups. These data are of interest to better understand the process of nerve conduction in the special sensory system.

We conducted a study to compare morphological characteristics of various nerve cells in the sensory system. This sort of evaluation is indispensable for a better understanding of the nervous system in relation to clinical physiology and neurology.

The number of people with functional disabilities has been increasing with the rapid changes of age structure in the overall population. One of the major causes of disturbances in daily activities is cervical spondylotic myelopathy (CSM). The transverse area and sagittal diameter of the spinal cord measured by MRI is reported to correlate with the clinical manifestations of CSM, the duration of the disease, and the speed of recovery after surgery in patients with CSM. The purpose of this research is to determine the morphological characteristics of CSM as seen in MRI findings including the spinal cord sagittal diameter, transverse diameter, transverse area and flatness ratio. Twenty-eight of several patients with CSM were treated conservatively after carrying out measurements by MRI. In addition, anatomical studies were carried out on the spinal cords after anatomical dissection of the vertebral column in seven cadavers with CSM. These results, when compared with the morphological analysis of the cervical spinal cord, show that there is a correlation between the transverse areas at C4, C5 and C6 levels, as those at every level of the cervical transverse areas of tissue sections in the dissection cadavers were 10-18% smaller than those in the MRI patients. These results should be taken into account for the treatment of CSM patients.

We morphologically evaluated the size of axons in the posterior funiculus in different age groups and examined the changes due to aging. In the past, such studies have been conducted at the cervical spinal cord (C6) level, and a decrease in the size and number of axons due to aging has been noted. The current study was conducted at the lower lumbar spinal cord (L2) level.

We compared morphological and morphometric data on various motor neurons in the human pyramidal system using the modified Klüver-Barrera staining method with extremely minimized shrinkage ratio and an image-analyzer. We classified motor neurons in the human pyramidal system into three groups according to the measurement data. This report may be of interest to better understand the process of nerve conduction in the human pyramidal system.

In order to study the precise structures of the human eyelids, we made serial sections, and found a plug-in structure protruding from the lacrimal caruncle and reaching into the lacrimal point. We will show a photo of this plug-in structure, as we believe it plays an important role in the lacrimal drainage system.

Myelinated axons in the human lateral corticospinal tract (LCST) at the C6 and L4 levels were examined on 16 male cadavers, with age ranging from 41 to 88 years. The average area of axons in the LCST was measured using a microscopic image-analyzing system. Our data show that the average area of axons at the C6 and L4 levels decreased with age. We also noticed that the average area of axons was larger at the C6 level than at the L4 level in all cases. This decrease may be related to a parallel decrease of conduction velocity in the LCST during the ageing process.

The morphometric features of the development of the human cuneatus medialis nucleus (CMN) were examined using complete serial celloidin sections of 11 brains: nine fetal brains, the brain of a 2-month-old infant and that of a 63-year-old adult. The morphometric analysis revealed at least four stages in the development of the CMN characterized by the maturation of neurons: (1) immature neuronal stage, (2) preparatory stage, (3) accelerated development stage and (4) postnatal stage. The development of the human CMN accelerates after 32 weeks of gestation (WG), and postnatal qualitative maturation also occurs. From the viewpoint of morphometric evaluation, the CMN gradually matures between 18 and 40 WG without a rapid growth phase as far as we have observed.

We examined the human mandibular nerve to find differences in the composition of nerve fiber axons between dentulous and edentulous jaws Using Goto's modification of Masson-Goldner's method. We discovered that the edentulous jaw did not contain any large size axons, compared with the dentulous jaw. This can be considered as evidence that the larger fibers innervating the periodontal ligament decreased degenerated after tooth loss.