Abstract
Fresh green plant material is frequently used to supplement standard stock diets in the raising of laboratory animals such as the rat. Recently, additional impetus has been given to the study of young green growing plants by observations on the previously unknown factor (factor pl of Wulzen and Bahrs, 1 grass juice factor of Kohler, et al. 2 , 3 , 4 ) necessary for the normal growth of guinea pigs 1-5 and on the nutritive value of cereal grasses. 6 Such studies would be greatly facilitated if it should be possible to grow young plants in the laboratory under reproducible conditions at any time and in the desired quantities.
A method has been developed in this laboratory for the purpose of adding the grass juice factor to relatively purified breeding diets for nutrition studies on mice which are handled with bacteriological precautions. The following qualities are essential: (a) a product which will provide a potent source of the grass juice factor, (b) uniform seed, (c) a nutrient solution composed of chemically pure ingredients, (d) a planting base which is as inert as possible, and (e) general cleanliness, with emphasis on freedom from insects, vermin and harmful bacteria.
After more than a year of study, the following method has been evolved and has proved satisfactory. It consists essentially of spreading soaked seeds on a layer of cotton placed on a screen which has been suspended over a pan containing nutrient solution. The roots grow down through the cotton. The grass begins to sprout within 24 hours after planting, and reaches a height of about 5 inches by the seventh day (Fig. 1).
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