长治市幼儿园4—5岁儿童四季生长情况

作者对山西省长治市幼儿园1980和1981年出生的216名儿童(男125、女91),在1985年四季生长的情况进行了测量和统计分析。结果表明,男童年均身高增长6.12厘米,体重增长2.49公斤;女童年均身高增长5.65厘米,体重增长2.35公斤。各季身高和体重增长值经F检验,季节差异均非常显著(p<0.01)。一年内最佳生长季节为秋季,同其它三季比较,经Dunnett检验,只有春季男女儿童身高增长和冬季女童体重增长与秋季相比,差异不显著(P<0.05)。其余各季增长同秋季比较,差异均非常显著(P<0.01)。     

THE FLOCCULATION OF GELATIN AT THE ISOELECTRIC POINT

The results of this investigation show that a gelatin solution consists of a considerable number of constituents. At a particular temperature, certain gelatin constituents tend to aggregate and to flocculate from solution. When these particular gelatin constituents have completely flocculated, no further change occurs in the system and an apparent equilibrium exists. This is not a dynamic equilibrium between the gelatin flocculate as a whole and the gelatin remaining in the solution but a steady state determined for that system by the temperature. It is also shown that gelatin can be separated into fractions in which the gelatin constituents are more nearly uniform and tend to flocculate over a much narrower temperature range. It should be possible to obtain a number of fractions in which all of the gelatin would flocculate at a definite temperature. The aggregation of the various gelatin constituents is presumably due to loss of thermal energy, and the temperature at which this occurs must be some function of the mass of the constituent. It is natural to assume, then, that the constituents which flocculate at a given temperature are larger than those which remain in solution at that temperature. Recently, Krishnamurti and Svedberg (1930) have obtained evidence with the ultra-centrifuge that the constituents of a gelatin solution are heterogeneous as to mass, even at a pH value at which there is no tendency toward aggregation. There is much reason to suppose that the gelatin constituents do not differ very greatly chemically since different fractions have the same refractive index and the same isoelectric point. The data as a whole are best explained by considering the gelatin constituents to be different degrees of association of the same or very similar molecular structural units. This is in agreement with Sheppard and Houck (1930), who consider that "the molecules of gelatin are fundamentally identical with those of collagen, the difference being only in the degree of association and orientation". Meyer and Mark (1928) have interpreted the x-ray data obtained from collagen as indicating that the micelles of the collagen fiber are built up of main valency chains of anhydro-amino acids. It may be supposed that during peptization of these fibers, the amino acid chains become separated, disorientated, and partially broken up, so producing the heterogeneous system which we know as gelatin. It is evident that the manner in which this breaking-up proceeds depends upon the chemical treatment previous to the peptization process and the gelatin produced from lime-treated collagen would be expected to differ from that from acid-treated collagen. From the results herein reported it seems evident that the technique of isoelectric flocculation of electrolyte-free gelatin offers a profitable method for the study of gelatin and an extended investigation along these lines should yield much valuable information concerning the nature of gelatin. It is possible that this method may also be extended to other hydrophilic colloids.     

DEVELOPMENT OF THE EGG OF THE MACKEREL AT DIFFERENT CONSTANT TEMPERATURES

1. Mackerel egg development was followed to hatching at constant temperatures of 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, and 24°C. Experiment showed that typical development could be realized only between 11° and 21°. 2. The length of the developmental period increases from 49.5 hours to 207 hours when the temperature is lowered from 21° to 10°C. 3. The calculated µ for the development of the mackerel egg is about 19,000 at temperatures above 15° and approximately 24,900 for temperatures below 15°C. 15° is, apparently, a critical temperature for this process. 4. The calculated values of µ for eight stages of development preceding hatching, i.e. 6 somites, 12 somites, 18 somites, 24 somites, three-quarters circles, four-fifths circles, five-sixths circles, and full circles, are essentially the same as the µ''s for hatching, indicating that the rate of differentiation up to hatching is governed by one process throughout. Critical temperatures for these stages approximate 15°. 5. The total mortality during the incubation period was least at 16°C. where it amounted to 43 per cent. At temperatures above and below this there was a steady increase in the percentage of mortality which reached 100 per cent at 10° and 21°.