THE ELECTRON MICROSCOPIC LOCALIZATION OF CHOLINESTERASE ACTIVITY IN THE CENTRAL NERVOUS SYSTEM OF AN INSECT, PERIPLANET A AMERICANAL.

The distribution of esterase activity in the last abdominal ganglion, the connectives and the cereal nerves of the cockroach Periplaneta americana has been investigated cytochemically. Activity of an unspecific eserine-insensitive esterase (or esterases) has been found in glial elements in these regions of the nerve cord. In addition, sites of cholinesterase (eserine-sensitive) activity have been found in association with (a) the glial sheaths of the axons in the cereal nerves and connectives, (b) the glial folds encapsulating the neuron perikarya in the ganglion, and (c) in localized areas along the membranes of axon branches within the neuropile, often flanked by focal clusters of synaptic vesicles. These results are discussed with particular reference to the previously reported insensitivity of the insect nerve cord to applied acetylcholine, and to the probable existence of a cholinergic synaptic mechanism in the central nervous system of this insect.     

FURTHER OBSERVATIONS ON THE STRUCTURE OF MYELIN SHEATHS IN THE CENTRAL NERVOUS SYSTEM

Direct evidence has been presented to confirm the existence of a spiral in the myelin sheaths of the central nervous system. An account of some of the variations in structure of central myelin sheaths has been given and it has been shown that the radial component of myelin sheaths has the form of a series of rod-like thickenings of the intraperiod line. These thickenings extend along the intraperiod line in a direction parallel to the length of the axon. The relative position of the internal mesaxon and external tongue of cytoplasm has been determined in a number of transverse sections of sheaths from the optic nerves of adult mice, adult rats, and young rats. In about 75 per cent of the mature sheaths examined, these two structures were found within the same quadrant of the sheath, so that the cytoplasm of the external tongue process tends to lie directly outside that associated with the internal mesaxon. The frequency with which the internal mesaxon and external tongue lie within the same quadrant of the sheath increases both with the age of the animal and with the number of lamellae present within a sheath. The possible significance of these findings is discussed.     

THE CENTRAL NERVOUS SYSTEM OF CHAMELEON VULGARIS

An analysis of the brain of Chameleon has given evidence of a number of modifications in the general plan of the reptilian nervous system. The telencephalon shows a reduced olfactory mechanism and suggests the presence of the true motor cortex. The ventral peduncle of the lateral forebrain bundle is unusually large with the majority of its fibres terminating in two new nuclear masses in the hypothalamus, the nucleus entopeduncularis, and a few in the nucleus ruber. A high degree of effective response to optic stimuli is indicated by the extensive correlation between the optic tectum and the nuclear masses of the midbrain and the diencephalon. The wide range of eye movements is probably correlated with the development of the basal optic root ganglion and its numerous secondary connections and the elaborate relationship of the geniculate complex. The usually highly developed tecto-bulbar system is partly replaced by a large tegmento-bulbar system that relays the tectal impulses caudally. An interesting mesencephalic nucleus is a large nucleus profundus mesencephali that receives a great variety of impulses and appears to be an important correlation center. Ascending visceral mechanisms were described bringing the hypothalamus into relationship with the lower centers. The great excursion of the tongue is associated with a highly differentiated hypoglossal nucleus. Components of the medial lemniscus from the spinal cord and the medulla to the vicinity of the thalamus were demonstrated.     

真水狼蛛纺器的扫描电镜观察

通过室内饲养,获得了不同龄期的真水狼蛛。对其纺器扫描电镜观察表明：真水狼蛛的纺器表面分布许多纺管,纺管的数目随着龄期的增大面增加。１龄幼蛛纺器分化没有完成。因而不能纺丝。雌蛛和雄蛛在纺器的排列位置、形态、纺管类型和纺管数目上都存在较大差异。纺器的形态、结构与纺器纺丝、结网的功能相适宜。     

细叶满江红大孢子果的扫描电镜观察

细叶满江红(Azolla filicufoides Lam.)是优良的水生绿肥和饲料作物,又是用孢子果越夏和过冬的好材料,植物学者对其进行广泛研究已有悠久的历史。本文记述了电镜扫描观察到的大孢子果及小孢子囊泡胶块的图象;认为大孢子果表面同小孢子囊泡胶块的附着力,与大孢子果的萌发力有相关性;指出孢子果带菌,将是导致高温季节大田满江红发生毁灭性病害“自然倒萍”的主要因素之一。     

ELECTRON MICROSCOPIC OBSERVATIONS OF THE OLFACTORY MUCOSA AND OLFACTORY NERVE

The olfactory receptor cell is characterized by a distal process (the dendrite) which terminates in the olfactory passage as the olfactory rod. The olfactory rod is provided with numerous cilia which are similar in structure to those seen in other tissues. The central processes of the bipolar cell constitute the fila olfactoria. The cytoplasmic organelles of the sustentacular cell are concentrated at the apical and basal ends of the cell with a paucity of cytoplasmic elements in the region of the nucleus. The plasma membrane of the supporting cell forms a mesaxon for both the dendrite and axon of the bipolar cell. Terminal bars are present in the epithelial cells. The axons constituting the fila olfactoria form fascicles which are ensheathed by mesaxons of adjacent Schwann cells. Thus the olfactory neurons are ensheathed throughout their course by the membranes of sustentacular and Schwann cells. Observations of the olfactory mucosa with the electron microscope are discussed with respect to recent electrophysiological studies.