A Discussion of Some of the Factors Causing Variable Results with Flagella Stains

Most flagella stains would probably give more consistent results if they were of stable composition and more was known of the factors influencing the mechanism of their action. Many of the mordants that have been recommended change rapidly, both chemically and physically, after preparation.

The reaction of some mordants, such as that of Loeffler, seems to be an important factor in their use. It is complicated, however, by temperature effects, oxidizing and reducing agents, the age of the bacterial cultures and variations in different species.

Users of flagella stains will probably always have to select or alter methods to suit the cultures to be stained. Any method which makes use of a minimum of complicated solutions and operations is most likely to give consistently good results.

No clearing or decolorizing agent tried changed poor preparations to good ones, but sometimes good ones can be improved by this treatment.     

Some Factors Causing Mortality among Female Minks during the Puerperium and Lactation Periods

The purpose of this study, in which the farm was used as the statistical unit, was to find factors affecting mink mortality under farm conditions. Mortality was hypothesised to be affected by factors including, among others, variables describing the amount (level) and variation in composition and quality of the feed. Other explanatory variables applied in the study included farm size and age. Factor analyses were performed for variables of feed composition and quality in order to condense the variable information and to facilitate the selection of explanatory variables. This report presents a preliminary regression model for female mink mortality factors describing feed level and variation, and farm size, as explanatory variables. The regression model emphasized among other factors the importance of a constant albumin quality and a constant energy level.     

Some Factors Causing Variability in 1,2-Dibromo-3-Chloropropane Concentrations in Soil

Relative to nematicides with greater fuming capabilities, 1,2-dibromo-3-chloropropane (DBCP) moved nonuniformly through soil. DBCP concentrations in soil were reduced by low soil temperature and the presence of lime or roots within the soil profile, Applications by either water or chisel injection provided DBCP movement to 120 cm and below. Concentrations were least persistent in the upper 15 cm of the field surface and in one situation where application was not followed by irrigation. Values for Henry''s Constant are reported for DBCP at a range of solution temperatures. Certain advantages and disadvantages of soil atmosphere sampling of DBCP are discussed.     

A Method for the Staining of Bacterial Flagella

A modification of the Loeffler method of staining bacterial flagella is proposed. The chief points of the modification are: The cultures are inoculated into distilled water after two successive daily transfers on agar slants, and the distilled water cultures are incubated at optimum temperature for from 48 to 72 hours. The mordant (tannic acid, ferrous sulphate, basic fuchsin) is allowed to stand 18 to 24 hours before use, and then cleared by centrifuging or filtering. An anilin water fuchsin is used as a stain. No heat is used for either mordanting or staining; but both mordant and stain are allowed to act on the preparation for 15 minutes. The writer finds the method admirably adapted for use in class work, where nearly 100 per cent success has been obtained except in the case of some three or four species of bacteria that are especially difficult to stain.     

A Method for the Staining of Bacterial Flagella

A modification of the Loeffler method of staining bacterial flagella is proposed. The chief points of the modification are: The cultures are inoculated into distilled water after two successive daily transfers on agar slants, and the distilled water cultures are incubated at optimum temperature for from 48 to 72 hours. The mordant (tannic acid, ferrous sulphate, basic fuchsin) is allowed to stand 18 to 24 hours before use, and then cleared by centrifuging or filtering. An anilin water fuchsin is used as a stain. No heat is used for either mordanting or staining; but both mordant and stain are allowed to act on the preparation for 15 minutes. The writer finds the method admirably adapted for use in class work, where nearly 100 per cent success has been obtained except in the case of some three or four species of bacteria that are especially difficult to stain.     

与中国现代人起源问题有联系的分子生物学研究成果的讨论

本文简略介绍最近几年发表的与中国现代人起源有直接和间接关系的几篇分子生物学论文,结合中国的人类化石、旧石器、古哺乳动物学和亚洲西部的旧石器以及分子生物学研究的新资料,论证根据Y染色体一些基因的分析认为中国的古老人类被来自非洲的现代人完全替代的推论不能成立。古人类学的研究已经显示人类进化是十分复杂的过程,新的分子生物学论文也显示人类的分子进化比过去认识的远为复杂。在对新信息进行解释和推论时必须对这样的复杂性保持深刻清醒的认识,人类进化不可能既是这样又是那样,只有将各个有关学科得来的信息进行综合思考才可望使得根据这些信息得出的推论趋于协调,对人类进化的认识逐渐接近真实。     

A Comparison of American Stains with Recent German Products

In 1947, 31 samples of stains of German manufacture were collected in that country, with the cooperation of the U. S. Department of Commerce and one of the American stain manufacturers. They have been compared with current American products by the same tests as used for the samples submitted for certification. Only two proved distinctly superior to the corresponding American dyes, three others as good as the best American samples, four proved entirely unsatisfactory, while seven others were abnormal from the spectrophotometric standpoint although performing satisfactorily when used in the staining procedures by which they were tested.     

Progress in the Standardization of Stains Certain Less Commonly Used Stains

The Commission must acknowledge the assistance recently given by two commercial concerns in developing two new products, namely, a pure type of hematein and a special grade of acid fuchsin.