Volume 13, Issue 1
January 1941, pages 1-84
pp 1-8 January 1941
The excitation of the optical modes of vibration of a crystal lattice by radiations incident on the crystal is discussed. The optical vibrations can be described as oscillations of the interpenetrating lattices in the crystal with respect to one another. They give rise to a periodic variation of the physical constants,e.g., electric dipole-moment, optical polarisabilities, structure amplitudes, which influence the behaviour of radiation in various ranges of frequency in its passage through the crystal. The phenomena observed in the different ranges of frequency have a common feature, namely that the incident radiation excites the crystal vibrations of which the phases are everywhere in coherent relationship with the phase of the radiation field. The scattering of light or the reflection of X-rays with change of frequency appears as the result of the phase of the lattice vibrations varying from point to point in such manner that the crystal is, in effect, an optically stratified medium giving a monochromatic reflection of the incident rays at the appropriate angle of incidence determined by the spacing of the stratifications and the wave-length of the incident radiation. The description of the observed effects in the language of the wave-theory and in terms of the quantum hypothesis are complementary and do not in any way contradict each other.
The paper includes a review of 14 communications dealing with this field of research published during the year 1940 in theProceedings of the Indian Academy of Sciences.
pp 9-23 January 1941
pp 24-32 January 1941
pp 33-34 January 1941
pp 35-47 January 1941
The Schiøtz tonometer and the Tycos aneroid sphygmomanometer are used to record the eye tension and the blood pressure of 465 subjects consisting of 170 healthy men, 40 healthy women, 208 pregnant women and 47 women after parturition. The results of the investigation are analysed to ascertain
the range of variation of normal eye tension in healthy men and women (average for men=19·12 mm. of Hg, σ=±2·90 mm. of Hg and for women=18·65 mm. of Hg, σ=±2·70 mm. of Hg the range being 10 mm, to 30 mm. of Hg);
the influence of age on the variations in eye tension and blood pressure, and their interrelationship;
the relation of the hypotony in pregnancy to the reduction in the systemic blood pressure.
The following observations and conclusions are drawn regarding (2) and (3):
The variations in the eye tension are opposite to those of the blood pressure in all age periods in both sexes, except in women between the ages 45 and 55 years—probably because of the endocrine disturbances accompanying the climacteric.
The eye tension and blood pressure are the lowest about the middle of pregnancy, both varying in a parallel manner from the start to the termination of pregnancy.
The factors influencing the eye tension and blood pressure in the last months of pregnancy have a greater depressing effect on the eye tension than on the blood pressure.
The bearing of (i), (ii) and (iii) on the humoral control of the maintenance and regulation of the normal intra-ocular pressure is discussed.
pp 48-59 January 1941
pp 60-70 January 1941
A species ofColletotrichum isolated fromCarthamus tinctorius was found to beC. capsici. This gave rise to several saltants in cultures. A comparative study of four of the saltants and the parent was made. The saltants showed differences in growth characters, size of acervuli, presence or absence of setæ and sporulation. The setæ were found to be of two kinds and the size was much affected by environment. The medium influenced the size and production of spores. Saltants differed in their pathogenic ability. It is suggested that in the creation of new species ofColletotrichum pathogenic capacity alone should not be given much prominence.C. capsici constantly gives rise to new races in cultures.
pp 71-83 January 1941
pp 84-84 January 1941 Erratum