Search

Eruption, attrition, and crown length were measured in impeded and unimpeded rat incisors in hypophysectomized and magnesium-deficient rats. The rate of unimpeded eruption was twice the rate of impeded eruption; this proves that the rates of eruption and attrition are determined by the amount of occlusal contact and the condition of the periodontal ligament.

The method is based on the assumption that the number of maggots of a group of dipterous parasites falling on a unit area of ground will be an index of the spruce budworm populations on the tree above that area. An analysis of 2 years' data indicated considerable variation in budworm population between trees. Budworm distribution within trees was markedly correlated with crown level the top third having the most larvae and, indirectly, the most maggots. Crown length provided good stratification for expressing and estimating budworm larvae and fly maggot populations. An estimate of significant differences between populations can be determined not only for any 2 years within the same area but also for any two areas during the same period.

Various dimensions such as crown length, crown width, crown thickness, root length and total length were measured in more than 3000 male teeth and in about the same number of female teeth. In the measurement, FUJITA'S standard method was employed. Through statistical treatments of the data, following results were obtained:(1) In general, the tooth size is larger in the male than in the female in every dimension of every tooth.(2) However, root length of the upper third molar presents an exception inasmuch as the female significantly surpasses the male. The lower third molar of the female is also superior to that of the male in its root length, although the difference is statistically not significant.(3) The sexual differences in size are not the same for all sorts of the teeth. It is most conspicuous in the upper and lower canines, while the incisors and the premolars show less difference both in the upper and the lower jaws.(4) Each dimension of the tooth shows different degree of sexual difference. It is greatest in root length and smallest in crown width.(5) As compared with the sexual differences in general constitution such as stature, body weight etc., the degree of the sexual differences of the teeth is somewhat smaller, whereas it is larger in root length.(6) It is not yet clear what the mentioned sexual differences mean. It might be surmized that the larger canine of the male represents the phylogenetical trace of the striking sexual difference prevailing in the animal kingdom.

SUMMARY This study deals with the growth distribution within the annual ring and with the influence of tree characteristics and stand density on diameter growth in two stands of P. radiata. An analysis of crown dimensions showed a curvilinear increase of crown length with DBH, a linear relationship between crown width and DBH and a slight decrease of the height above ground of the crown base with increasing DBH. The relative position of the point of the greatest crown width was not related to DBH. The South-Eastern winds, prevailing during summer, cause crown deformations. The smallest crown radius occurs on the South-Eastern and the largest radius on the North-Western side of the trees. Within the tree, diameter growth is directly related to crown radius, but for the same crown radius, the growth on the North-Western side of the stem exceeds that on the South-Eastern side. This might be explained in terms of a reduced photosynthetic output per unit leaf surface on the windward side or alternatively in te...

Crevice depth and clinical crown length have been measured pre- and postoperatively after marginal flap procedure in apicoectomies performed in 15 patients. The crown length was assessed by plaster models and the crevice depth by insertion of thin celluloid strips into the gingival crevice. No changes were found in crevice depths, but an average gingival retraction of about 0.5 mm was recorded at follow-up 3 months after surgery. Based on these findings the author recommends a trapezoid incision placed 5 mm from the marginal gingiva.

Comparison is made of the population of ospreys in Cape May County, N.J., in the late 1930’s with that in 1963, and with a population of these birds at Tilghman Island, Maryland. Production of young per nest in the 1930’s compares favorably with the production of young in the populations examined in 1963. It is suggested, based on historical evidence, that a decline in the numbers of these birds has been going on for some time. Acceleration of this decline in New Jersey is more obvious in the years covered by this paper.