Biomedical subjects
Publications and source records attributed to S R Cobb.
The spectral absorption curve of 'red' cones erytholabe and the 'green' cones chlorolabe are examined by these techniques. Evidence is elicited for a fourth photopic response peaking at approximately 570 nm.
The Unique Green phenomenon whereby the wavelengths of light which are judged neither blue-green nor yellow-green show a distinct genetic polymorph. Amongst the males there is a clear bimodality whereas there is a near normal distribution amongst the females. The classification of the types of person so produced breeds true apparently in the X-chromosome. This phenomenon now having been confirmed is impossible to fit into the strict Walraven model of colour vision without modification. The modification that would be used is discussed and it is shown that a number of other difficulties within the Walraven model model can also be resolved.
This paper discusses whether defective colour vision affects the type of personality of the individual. Three pieces of recent research are examined. Pickford and Cobb (1974) found a positive relation between colour defect and type of personality when they tested a sample of students in psychology. However, two later studies of school children did not demonstrate such a relationship. It is postulated that the contradiction in results between the first and the last two studies can be explained by the assumption that the effects of colour defect on the personality do not occur until later in life.
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This paper discusses the possibility there is a difference between men and women in foveal tritanopia. The discussion is based on a study carried out by Cobb and McCrossan in 1973 in which they measured the luminosity curves of the fovea in five women and five men. The instrument used was a Wright colorimeter which measured the luminosity curves with a 2 degree 12' field and a 0 degree 12.5' field. Comparison shows a loss of sensitivity to blue for the curve obtained with the 0 degrees 12.5 relative to the curve obtained with the 2 degree 12' field. Male subjects obtained two maxima with the 0 degree 12.5' field, usually at 555 nm and 595 nm, whereas for females on maximum, usually at 555 nm and from 555 nm to the long wavelength end of the spectrum, curves followed loosely the curve obtained with the 2 degree 12' field. Thus, a significant difference was found between the males and the females in their response to the longer wave-lengths when the 0 degree 12.5' (0 degree 12.5') field was used. In addition to this there were also large individual differences in the matching points obtained by the males while the differences among the females were much smaller.
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Astigmats, who have been fully optically corrected, show an acuity configuration highly characteristic of the uncorrected astigmatism when they are tested with gratings of different orientations. This phenomenon, which is called meridional amblyopia, has been supposed to be neural in origin. This paper attempts to show that there is evidence for a critical period in the visual system of humans. In the experiment described here twelve astigmatic subjects were tested against a control group of six non-astigmatic (emmetropic) subjects. The astigmatic subjects differed in the ages at which they had been initially optically corrected. Square-wave gratings were used to test the subjects and measures of acuity for different orientations were recorded. It was found that those astigmatic subjects corrected above the age of seven showed the usual acuity decrement while those corrected below seven showed significantly smaller meridional amblyopia. The age of seven, therefore, was taken to mark the end of a critical period in the development of the human visual system, after which the system ceases to be structurally influenced by visual input.
An experiment whereby a standard filled circle is exposed for 100-1000 msec on the tachistoscope for ten subjects. Each is asked to choose a comparison circle, which appears to be the same size, out of a series of eleven filled circles of various angular subtenses larger and smaller than the standard filled circle in the tachistoscope. The results indicate that exposure time has a role in the perception of size.
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The mode of inheritance of the Unique Green phenomenon is investigated by a new technique. This involves a spectrometer which generates the stimulus in such a manner that the exact position that is neither blue-green nor yellow-green can be compared with neighbouring positions in the spectrum. This technique is used in conjunction with the single field techniques of Waaler to confrim the mode in inheritance he has suggested: that it is an effect carried on the X chromosome. The placing of the Unique Green point in the spectrum is shown to correlate with the mid-matching point in the blue-yellow axis on the Pickford Nicolson Anomaloscope. It is concluded that there may be a highly photolabile visual pigment present, which absorbs maximally at about the yellow region of the spectrum,
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The rate of mongolism is well known to increase with maternal age and has been suggested by German to be connected with the frequency of intercourse. The occurrence is discussed in relation to the possible use of vaginal lubricants as a consequence of deficient cervical and Bartholin secretion. The implications of this idea are discussed.
The CT scans of 10 traumatized patients with demonstrable ocular injuries were reviewed. The CT findings were correlated with the clinical findings in each case. CT manifestations of a variety of ocular and orbital injuries are reported and a systematic approach to the CT evaluation of ocular trauma is presented.
A number of CT head scans, covering a 2-year period and showing a variety of distinct curvilinear subinsular lucent lesions, were collected and reviewed. Variations in extent of involvement, tendency toward bilateral symmetry, and clinical background allowed the lesions to be grouped into four general patterns, most of which, to our knowledge, have not been specifically described in the radiologic literature. This project was undertaken first to bring to the attention of those involved in interpretation of cranial CT images several patterns of injury they may not heretofore have been aware of and second to attempt to derive a specific etiology for each of the patterns described. Pattern 1, which appears as a distinct curvilinear lesion (sometimes cystic) apparently limited to the lateral aspect of the putamen, is thought to represent the residua of previous lateral striatal hemorrhage. Pattern 2, occurring in a markedly younger age group appears as relatively symmetrical bilateral subinsular lucencies, which in one case completely resolved. A specific etiology for this pattern remains uncertain. Acute demyelination, either secondary to a variant of anoxic leukoencephalopathy or to a limited form of diffuse encephalomyelitis, is postulated. A third pattern, which extends from generalized deep frontal white-matter lucency across the anterior limb of the internal capsule and tapering posteriorly in the subinsular area is thought to be on the basis of chronic ischemia similar to subcortical arteriosclerotic encephalopathy. The fourth pattern, occurring as a broad band of lucency extending from the frontal horn of the lateral ventricle and also tapering posteriorly is due to relatively proximal occlusion of the lateral lenticulostriate arteries.