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SummaryPlatelet function has been evaluated by Hellem’s original method in carefully screened normal persons of various ages. Factors which could possibly influence platelet behaviour, such as drugs, smoking, hypercholesteremia, prediabetes, hypertension or uremia were excluded in preliminary examinations. Only individuals in perfect health without a history of coronary heart disease, peripheral vascular disease or other thrombotic disorders were selected. Physical activity did correspond to the age. Variation in results possibly due to technical factors were eliminated by using strictly the same method and material throughout the study and by performing the tests within a relatively short period of time. From an original group of 109 normal persons, 70 individuals between the ages of 10 and 90, who corresponded to the described standards were chosen for further trials. They were divided into 7 age groups, each including 10 individuals within a decade (the last group ranging from 70 to 90 years). Retention of platelets in a column of glass beads was measured by Hellem5s method. The results, expressed as per cent retention and represented graphically, form a parabolic curve with its minimum at the age of 35 (mean ± 2 SD = 50 i 22%). The mathematical function of the curve can be expressed in a formula as second degree polynomial. It is shown by analysis of variance that age is the only factor on which the slope of the curve depends. Physiological or pathological implications of these findings are not known. The results, however, show that age must be taken into account when differences of platelet behaviour are discussed.

Les Entomophthoroses sont endemiques, toute l'annee, dans les populations de pucerons anholocycliques de l'Ouest de la France et elles donnent lieu a des epizooties qui, sur Feverole, par exemple, aneantissent tous les ans, les colonies d'Aphis fabae en quelques jours. De telles epizooties ont aussi ete notees surCapitophorus horni, sur Artichaut, en Bretagne et surMyzus persicae, sur Pecher, dans la vallee du Rhone.

Le puceronCapitophorus horni peut causer de graves prejudices aux cultures d’artichauts dans l’Ouest de la France. La presente note fait l’inventaire des parasites (Aphidiides et Entomophthorales) de cet aphide et precise leur role dans la regulation de ses populations.

L’etude comparee de la capacite vectrice de larves du 4e stade d’apteres, de nymphes des 3e et 4e stades d’ailes, d’adultes virginipares apteres et ailes d’une souche d’Aulacorthum solani, deMacrosiphum euphorbiae et deMyzus persicae a ete realisee surSolanum tuberosum var.Claudia. Il ressort que les categories les plus efficaces sont les nymphes et les adultes apteres d’A. solani et les larves du 4e stade d’apteres deM. euphorbiae et deM. persicae; les categories les moins efficaces sont respectivement les larves du 4e stade d’apteres d’A. solani, les nymphes deM. euphorbiae et les adultes ailes deM. persicae.

Des transmissions de l’Enroulement ont ete realisees sur germes deClaudia a 6, 15 et 24°, a l’aide de pucerons appartenant aux especesA. solani, M. euphorbiae etM. persicae. Il ressort que la transmission est d’autant plus elevee que la temperature est plus forte, le taux de cette augmentation n’etant pas le meme pour les divers stades, formes, souches de pucerons. De plus dans le cas des nymphes, il y a reduction du pourcentage de transmission lorsqu’apres une temperature de transmission de 24°, on applique des temperatures de 6 ou 15°. Il y a augmentation quand on soumet les tubercules a 15 ou 24° apres une temperature de transmission de 6°.

Le declenchement depizooties au sein de populations d'Aphis fabae sur feverole de printemps est largement du aux facteurs climatiques et dependant de l'hote. Trois annees d'experimentations ont permis de preciser ces facteurs en conditions naturelles.

Des demi-tubercules germes de pomme de terre de varieteClaudia ont ete utilises pour comparer la capacite vectrice de 5 souches d'A. solani et deM. persicae, de 5 souches vertes et d'une souche rose deM. euphorbiae. Toutes les souches d'A. solani et deM. persicae contre une seule souche (verte) deM. euphorbiae ont transmis le virus avec des differences entre souches plus ou moins importantes. L'importance epidemiologique de ces premiers resultats est discutee.

world, but in terms of the goals of analysis, which are explanatory and predictive power. Although Awh suggests the contrary, economists do not concentrate on the pricequantity relationship because they believe a given percentage change in the price will have a greater impact on quantity than an equal percentage change in, for example, income; the concept of elasticity, with the possibility that the coefficient is close to zero, should suggest this. (Awh writes: "The conventional treatment of the concept of demand probably is supported by the tacit assumption of the predominant importance of price. Price is considered to be either the most readily manipulatable variable or the most significant affecting the quantity purchased" [1, p. 19].) The most compelling reason for the emphasis is that the law of demand is the strongest statement which economists can make concerning human behavior. Economists can say with an extremely high degree of confidence that consumers will buy more if the price is lowered. They do not hold to any other relationship with the same level of confidence. In addition, a function of microeconomic analysis is to demonstrate how the pricing system and a competitive market structure can lead to an efficient allocation of

Introduction The differential diagnosis of melanoma cells in tissue cultures of uveal melanomas may present difficulties. Their growth patterns and morphological characteristics were reported in the preceding paper,1but since the morphology is not always clearcut, it was felt that the routine use of differential stains and histochemical reactions could be a valuable diagnostic adjunct. In an effort to determine what stains and histochemical reactions might best be suited to this purpose, a series of experiments was performed on melanoma cells from various sources. In addition to studies of variously stained preparations, a special study of the use of silver stains was undertaken. Of the many properties that have been used to identify melanin (color, site of formation, state of aggregation, mechanism of production, nature of the chromagen, solubility, chemical reactivity, composition), none is specific.2The most reliable of these differentiating properties, however, is chemical reactivity, i.e., the