Different parts of the cochlea were destroyed in 6 cats (11 sides). The degenerating fibers and preterminal degenerations were studied by the Nauta technique with the following conclusions: 1. The overwhelming majority of the fibers from the spiral ganglion project to within the limit of the cochlear nucleus complex. No fiber degeneration could be found in the trapezoid body. A few degenerating fibers from the basal turn of the spiral ganglion, however, were found in the dorsal acoustic stria. 2. No preteriminal degeneration was found in the “granular cell masses” and “dorsal cell complex of the acoustic tubercle”of G. Fuse. 3. In the dorsal cochlear nucleus, degenerating fibers were found to terminate in the II-V layers. 4. Contrary to Lorente de No’s finding, the present study showed that the fibers from the basal portion of the spiral ganglion bifurcate at the dorsal part of the ventral cochlear nucleus, those from the apical portion at the ventral part. 5. The spiral ganglion projects in a clear-cut topographical way to the 3 parts of the cochlear nucleus complex, viz, the basal portion and the successively more apical portions of the spiral ganglion project (a) to the dorso-medial and successively more ventro-lateral parts of the dorsal cochlear nucleus; (b) to the anterior part of the ventral cochlear nucleus along the dorso-caudo-medial to ventro-rostro-lateral axis; and (c) to the posterior part of the ventral cochlear nucleus along the dorso-rostro-medial to ventro-caudo-lateral axis.

After injecting the posterior pituitery of the albino rats with cholera-toxinconjugated HRP,retrogradely labeled neurons were found in the area of the bednuclei of the stria terminalis (BST),which were then analyzed,based on therecent cytoarchitectonical study of the BST.In the anterior subdivision of the BSTdendrites could be seen in the parastrial nucleus with a few labeled cells surround-ing it;cells of the magnocellular nucleus were found scattered in the subdivision;some labeled cells were also identified in the ventral nucleus.Surrounding the dor-sal half of the posterior division of the BST there were several fairly distinct labe-led cell groups,viz.,the anterior fornical nucleus,medial and lateral dorsal accessorygroups,and the subinterventricular group.Though these cell groups are contiguouswith the BST,they do not seem to belong to the BST itself,but their dendritesoften extend into the posterior division of the BST,thus sharing some commonafferents with the latter.A few less constant cells were sometimes seen scattered invarious parts of the BST.

Horseradish peroxidase was injected into C_(6,7) or L_(5,6) spinal cord in 21 adult cats and the morphology and distribution of the labeled cells in the dorsal columu nuclei (DCN) were studied. Cells projecting to the cervical cord were found to be distributed mainly in a region from 2.5mm below to 0.5mm above the obex, while cells projecting to the lumbar cord were found within 2.5mm below the obex. Medio-Iaterally, the cervical projecting cells were located chiefly at the junctional area between the gracile and medial cuneate nuclei and at the ventromedial part of the latter. The lumbar projection cells were located more medially, concentrating at the junctional area and the ventrolateral part of the gracile nucleus. In both cases scattered cells were found in the two dorsal column nuclei. The difference in cellular distribution between cervical and lumbar injection cases is consistent with a somatotopical organization.The labeled cells in the dorsal column nuclei varied in shape and size. Small cells, mostly fusiform, were concentrated at the junctional area between the gracile and medial cuneate nuclei. Large cells were found scattered in the two nuclei. Many of them were triangular or multipolar with long and straight dendrites. A few were round and their dendrites bushy.

HRP was injected into the cervical or lumbar spinal cord in 8 adult cats. The anterogradely labeled terminal arborization and its relation with the retrogradely labeled cells in the DCN were studied.The non-primary afferent fibers were distributed diffusely in the DCN. Injection of HRP in one spinal segment, either cervical or lumbar, resulted in labeling of terminal branches throughout the rostrocaudal extent of the DCN. In C6 or C7 injection cases large amount of labeled terminal branches were found in the medial cuneate nucleus, chiefly in its extraclusteral regions, viz. in the rostral part and in the ventral area of the caudal two thirds of the nucleus. A small celled area at the dorsolateral brim of the middle part of the medial cuneate nucleus was found to approach and to be contiguous with the external cuneate nucleus at higher level. This area was likewise densely labeled. Labeled terminal branches were also found in the gracile nucleus in lesser amount.After L5 or L6 injections the labeled terminals were much less in amount than in cervical injection cases. They were distributed mainly in the gracile nucleus. In the lower part of the nucleus the labeled terminals were found in its dorsal, medial, and ventrar areas. In the upper part of the nucleus they projected diffusely. A slight degree of labeling was also found in the ventromedial angle of the medial cuneate nucleus.The areas of distribution of the labeled terminals and labeled cells overlapped but did not coincide with eachother. No or merely a few labeled terminals were found around some of the labeled cells, while other cells were located right in the center of heaviest terminal labeling with abundant terminal branches surrounding their somata and dendrites. This proved that the non-primary afferent fibers of the DCN might form monosynaptic feed-back loop with the DGN-spinal cells.

HRP was injected into the cervical or lumbar spinal cord in 8 cats and the spinobrainstem projections were traced with the anterograde HRP technique. The labeled terminal branches were found most densely concentrated in the ipsilateral dorsal column nuclei and lateral reticular nucleus, the contralateral medial and dorsal accessory olivary nuclei and the bilateral pontobulbar bodies and dorsolateral part of pontine nuclei. In the reticular formation and a number of brainstem nuclei labeled terminals were also found to varying degrees. The most remote site found labeled was the hypothalamus.It was also found that the dorsal accessory olivary nucleus could be further subdivided into a caudal and an oral part, cells in the caudal part being smaller than that in the oral one.In the accessory olivary nuclei labeled terminal branches were more numerous in lumbar injection cases. Clearcut somatotopical localization was demonstrated in the oral part of the dorsal accessory olivary nucleus.In the lateral reticular nucleus the subnucleus magonocellularis and the lateral wing of the subnucleus parvocellularis were the major sites of labeling and the labeling in cervical injection cases greatly out numbered that in lumbar injections.The cervical and lumbar injections were equal in their amount of projection to the pontobulbar bodies and the dorso-lateral part of the pontine nuclei.The distribution of spinal afferents in the inferior olivary nucleus, the lateral reticular nucleus, the pontobulbar body and the pontine nucleus was discussed.

The projection from the vestibular nuclei to the dorsal horn of the spinal cord in the cat was studied with the horseradish peroxidase method. It has been discovered that the vestibulospinal tracts originate not only from the lateral, medial, and spinal vestibular nuclei but also from the superior vestibular nucleus. The site of termination of the vestibulospinal tracts is in the lateral region of the dorsal horn of the spinal cord as well as in the laminae Ⅶ and Ⅷ of Rexed.

The brainstems of 6 rabbits were cut transversely in series and stained fornerve cells or myelin.The architecture of the parabrachial nucleus was studied.Be-sides general observation the length and width of 100 nerve cells in each of the 5nuclear areas chosen were measured and analysed statistically with the help of adigital computer.The following items were calculated:ratio of length to width,itsmean and 95% tolerance interval;area of nerve cells,its mean and 95% toleranceinterval;80% elliptical contour of normal bivariates for the length and width of thecells;cluster analysis of the more dispersed nuclear areas and 80% elliptical contourof each cluster. We concluded that the parabrachial complex consists mainly of 3 nuclei,viz.medial parabrachial nucleus,lateral parabrachial nucleus and magnocellularparabrachial nucleus.Dorsal to the medial parabrachial nucleus there is asmall area,which was tentatively called“d”area in the present study.The medial parabrachial nucleus lies medial to the brachium conjunctivum.Its cells are more or less round in shape,varying markedly in size and canbe clustered into 3 groups according to their size.The lateral parabrachial nucleusis located lateral to the brachium conjunctivum.Its cells are smaller than those ofthe medial nucleus,mostly spindle in shape.Some larger cells can also be seen scat-tered among the smaller ones and the process of clustering has yielded 2 groups ofcells.The magnocellular parabrachial nucleus can be seen in the middle range ofthe nuclear complex.It lies ventrolateral to the brachium conjunctivum with denselypacked large round cells.Its demarkation with the surroundings is sharp.A dorsalextension of this nucleus can be seen wedging between the brachium conjunctivumand the lateral parabrachial nucleus.Its cells are also large and compacted but arespindle in shape.Cells of the“d”area are small and round.Its relation with eitherthe medial or the lateral parabrachial nucleus remain unsettled.The relation between the parabrachial nucleus and the K(?)lliker-Fuse nucleuswas discussed.

The dorsal accessory olivary nucleus was studied with electron microscope in seven rabbits.The axo-axonal synapses,an axon being in contact synaptically with a spine of a perikaryon,the glomerulus with an axonal core and a bundle of microfibers within a nucleus of a neuron,as well as the already discovered axo- dendritic synapses,axo-somatic synapses and glomeruli with dendritic cores,were observed in this nucleus. The axo-dendritic synapses were often seen,the postsynaptic components of them were dendrites or spines.The axo-somatic synapses were fewer.An axonal terminal was seen synapsing to both a spine of a perikaryon and a dendrite.Both the presynaptic and postsynaptic components of the axo-axonal synapses contained spherical vesicles.Sometimes the axo-axo-dendritic synapses were observed.There were two kinds of glomeruli in this nucleus,one with dendritic core and the other axonal core.Two axons were discovered simultaneously synapsing with an axon. The complex synaptic pattern in the dorsal accessory olivary nucleus indicated that the afferent impulses would undergo diffusing,converging,presynaptic inhibition or integrating in this nucleus.

Cytoarchitecture of the ventrolateral superficial area of the medulla was studied on normal rabbit Nissl sections.There was a superficial area of small and medium sized cells,mostly fusiform,lateral to the pyramid.In middle and upper parts of the medulla superficial cells were also found in less amount in more lateral regions. At the middle medullary level there was a band of cells about 300 ?m from the surface with medium sized ones as its most prominent elements. HRP or WGA-HRP was injected in 10 rabbits into the cervical,thoracic or lumbar spinal cord unilaterally and its connection with the ventrolateral superficial area of the medulla was traced.Labeled cells were found in all cases along the pyramid.The lateral part of the superficial area was less labeled.The medium sized cell band at the middle medulla was markedly labeled,especially in thoracic injec- tion cases.More labeled cells were found in cervical injection cases in an area ventromedial to the facial nucleus. Anterogradely labeled terminal arborizations were in general small in amount, somewhat more prominent in cervical cases. The relation between the ventrolateral superficial area and the chemosensitive area is disscussed.

A glucose oxidase-3,3′ diaminobenzidine-nickel method was developed.Thistechnique can successfully demonstrate the details of the immunoreactive structuresand PHA-L labeled cell bodies and their processes.It is especially beneficial forvisualizing fibers and terminals.It is more sensitive than the regular 3,3′ diamino-benzidine method and the glucose oxidase-3,3′ diaminobenzidine technique,andvery stabilized.