Search

The main conclusions rest on the results obtained by ablating the superior colliculus in eight tree shrews. Additional animals either normal or with lesions of the superior collculus or striate cortex were studied to support or extend the basic findings. All eight tree shrews showed a profound loss of pattern discrimination which could not be attributed to some general factor such as inattention or an incapacity to learn. Thus, all succeeded in discriminating differences in the orientation of stripes but all failed to learn a habit based on discriminating the orientation of triangles. Two of the eight appeared normal in their capacity to orient toward, follow and track objects on the basis of vision. Six of the eight showed a remarkable unresponsiveness to visual stimuli manifested by a failure to follow, track, orient or even avoid what normal animals would regard as a threatening stimulus. This difference was clearly related to the extent of the lesion. In the two cases with normal visually guided behavior only the superficial three layers of the superior colliculus were removed. In the six cases with visual neglect the lesions included the deeper layers of the superior colliculus and invaded adjacent structures, notably the pretectum. It was concluded on the basis of differences between superficial and deep layers in their connections and in the behavioral effects of their ablation that the superior colliculus consists of at least two subdivisions.

Histological study of the masticatory muscles of the tree shrew showed that 140 muscle spindles are concentrated in the restricted areas of the inner lowermost layer of the horizontal and vertical portions of the temporal muscle (48 and 47 spindles, respectively), the profundus portion of the masseter muscle (42 spindles), and the zygomaticomandibular muscle (3 spindles). The medial and lateral pterygoid muscles are devoid of spindles.

The distribution of radioactivity after the injection of [3H] estradiol-17β has been studied in the tree shrew (Tupaia glis), using dry-mount and thaw-mount autoradiography in conjunction with thin-layer chromatography. [3H] estradiol is concentrated and retained in nuclei of certain neurons which are accumulated in selective areas of the phylogenetically old periventricular brain, including rhinencephalic, limbic, and brainstem structures. An atlas of the topographic distribution of estrogen concentrating neurons is provided. The pattern of distribution in the preoptico-strial, basal hypothalamic, and amygdaloid region is similar to the pattern reported earlier for the rat, mouse, guinea pig, squirrel monkey, and ring dove.

The efferent projection fibers from the olfactory bulb have been studied using the Nauta-Gygax and the Fink-Heimer methods for degenerating axons after lesions were suitably placed by thermo-coagulation. From the olfactory bulb efferent fibers by way of the ipsilateral lateral olfactory tract end as preterminal and terminal fibers in the lateral, the external and the ventral segments of the anterior olfactory nucleus; the lateral two-thirds of the lateral olfactory tract, the cortical and the medial nuclei of the amygdaloid complex.

Our evidence from both cytoarchitecture and studies of connections suggests that LE GROS CLARK was correct in postulating that the lateral posterior nucleus of primitive mammals is the homologue to the primate pulvinar. It seems evident that during mammalian evolution both this region of the thalamus and its cortical target have grown larger and more complex. Truly intrinsic subdivisions may have appeared not only in the primates but also independently in other mammalian lines of descent, such as the carnivores. One main goal of our laboratory is to ask how functional subdivisions are related to the increasing subdivisions of structure. Our hope is that this line of inquiry might contribute to an understanding of those functions most recently evolved in mammalian evolution.

Somatic sensory-motor area I, somatic sensory-motor area II, somatic motor-sensory area I and the areas of visual and auditory response were identified in the cerebral neocortex of the primitive placental mammal, Tupaia. Representation accorded with the general schema found in other small placentals and did not approximate more closely the patterns found in marsupials or monotremes. Overlap was found among areas. Slight cortical indentations and eminences appeared related to patterns of localization. Visual responses were extensive, variable and difficult to localize. It was not possible to distinguish MsI from SmI within the broad band of overlap among the Rolandic homologue, and it is suggested that this band is an indivisible region of somatic sensorimotor function. Cortical recording with fixed electrode arrays upon peripheral stimulation showed widespread, large, fluctuant, secondary responses which varied with the level of pentobarbital anesthesia.

The retinopretectal projection was investigated in the rat, mouse, rabbit and tree shrew primarily by means of the Fink-Heimer technique. The experimental animals survived for varying periods of time following unilateral eye removal. The retinopretectal projection in each species was predominantly contralateral. A dense field of terminal degeneration was observed in the nucleus of the optic tract and in the olivary pretectal nucleus in each of the species. A less dense projection was observed for the posterior pretectal nucleus in each species. A sparse projection to the anterior pretectal nucleus was observed in the rabbit and tree shrew but not in the rat or mouse. A dense, ipsilateral projection to the olivary pretectal nucleus was observed in the rat, mouse and tree shrew. A sparse, ipsilateral projection was found in the anterior end of the posterior pretectal nucleus in the rat, mouse and tree shrew and in the posterior part of this nucleus in the rabbit. In the tree shrew, a small amount of terminal degeneration was found in the ipsilateral anterior pretectal nucleus. The nomenclature used here is uniformly applicable among the species described.

Two tree shrews were tested on discrimination ofsuccessively finer stripes following ablation of striate cortex. Their postoperative threshold performance of 75% correct on 1/16

The distribution of melanotic melanocytes in the skin of the squirrel monkey (Saimiri sciurea) is similar to that of the Cercopithecoidea studied. However, the arrangement of hair follicles, the number of hairs in the hair groups, and the presence of alkaline phosphatase in the peripheries of sebaceous acini resemble more those of the tree shrew (Tupaia glis) and owl monkey (Aotus trivirgatus). The absence of eccrine sweat glands from the hairy skin and the aggregation of apocrine sweat glands in the chest in the squirrel monkey resemble those found in the blackcollared tamarin (Tamarinus nigricollis) and owl monkey. The most outstanding peculiarities of the skin of the squirrel monkey are: (1) the presence of butyrylcholinesterase-rich papillary nerve end-organs in the friction surfaces and (2) hair follicle nerve end-organs which are surrounded by melanotic melanocytes.

Previous studies have shown that treeshrews without striate cortex can easily discriminate between two simple patterns presented simultaneously. It has been suggested that these animals cannot actually ''identify'' patterns without striate cortex, but simply detect differences between two stimuli by scanning. The present study showed that tree shrews with damage to striate cortex, including complete removal, can discriminate horizontal from vertical stripes when presented either simultaneously or successively. This result supports the view that tree shrews do have the capacity to identify patterns in the absence of striate cortex. The present study also showed that tree shrews can perform the same discrimination following damage to the temporal cortex. However, if the lesion included all of the striate cortex plus a large amount of temporal cortex, the animals failed to discriminate the orientation of stripes even when they were displayed simultaneously.

Our evidence from both cytoarchitecture and studies of connections suggests that LE GROS CLARK was correct in postulating that the lateral posterior nucleus of primitive mammals is the homologue to the primate pulvinar. It seems evident that during mammalian evolution both this region of the thalamus and its cortical target have grown larger and more complex. Truly intrinsic subdivisions may have appeared not only in the primates but also independently in other mammalian lines of descent, such as the carnivores. One main goal of our laboratory is to ask how functional subdivisions are related to the increasing subdivisions of structure. Our hope is that this line of inquiry might contribute to an understanding of those functions most recently evolved in mammalian evolution.

Polygraphic activity was recorded and behavioral observations made during spontaneous sleep and wakefulness in six tree shrews (Tupaia glis). Four distinct states could be distinguis

The morphology and histology of the olfactory organ will be studied in Tupaia glis. The tree shrew shows all features characteristic for macrosmatic mammals. In this respect it is different from micro

Superficial lesions of the superior colliculus produced deficits in form discrimination, while deeper lesions produced, in addition, an inability to track objects. These two syndromes were related to an anatomical subdivision: Superficial lesions resulted in anterograde degeneration in the visual thalamus, whereas lesions confined to the deeper layers produced degeneration in the nonvisual thalamus and in brainstem motor areas.

The olivary pretectal nucleus has been shown to exist in the tree shrew and rat, in which it receives a dense projection of retinal axons. The nucleus is present in the pretectal region of other mamma

During the course of plague investigations carried out in Kenya Colony in 1921 by the late Dr. R. Van Someren, and in Uganda during 1922 by the same collector in conjunction with Dr. C. A. Baker, some hundreds of Mallophaga and Anoplura were collected, mainly from small rodents. This material was sent to the Imperial Bureau of Entomology in two instalments, and the present paper deals only with a new species and variety represented in the first collection forwarded by Mr. T. J. Anderson, Government Entomologist, Nairobi. The rest of the collection will be dealt with later. The opportunity has been taken to add also the description of a very remarkable louse which infests an Indian tree shrew.

Examination of the endoparasites and stomach contents of Moonrats and Pentail treeshrews helps to establish certain facts as to the behaviour and food preference in their natural environment. Earthworms and arthropods are the main diet of Moonrats in the wild, with fish, crabs and land molluscs as supplementary food. In captivity, this animal fed primarily on fresh fish. The Pentail tree-shrews, on the other hand are more insectivorous although meat is occasionally eaten. This animal apparently is not strictly a canopydweller as was previously believed. The stomach contents, and the fact that some specimens were trapped on the forest floor indicates that they may often descend to ground level.

Two types of hair changes occurred in an experimental group of captive tree shrews (Tupaia glis) living on an artificial diet in dark laboratory quarters. The most common variation in the fur consisted of a gradual type of hair loss resulting in a sparse coat and dry skin. The second type of hair change occurred in a female tree shrew in which patches of hair fell out all over the body. White hair regrowth followed exposure to sunlight, with subsequent repigmentation of the bases of the new hairs. Tree shrews suffering from the first type of hair disorder also improved when exposed to sunlight.

A completely automated free-field sound-localization apparatus is described along with a behavioral technique that provides several advantages over previously available methods. With the apparatus, the ability to localize the source of a sound has been tested in a wide variety of mammals including cats, rats, squirrel monkeys, hedgehogs, and tree shews.

1. 1. The mean day-night difference of body temperature in Tupaia glisis 5-1°C. 2. 2. The nocturnal standard metabolic rate is 0.76 ml O 2 /g per hr ± 0.07 (2 S.E.) at a mean body temperature of 37.0°C. 3. 3. The thermal neutral zone extends from near 30 to above 37°C. 4. 4. The marked decline in body temperature at lower ambient temperatures is interpreted to reflect the tropical habitation of this species.