A pigmented gelatin mass for vascular injection.

Almost any study of fine or coarse vascular anatomy or pathology can be assisted at some phase by the use of one or more of the various vascular injection techniques. Gelatin, which is superior for demonstration of vessels of microscopic and near-microscopic dimensions, is so rarely used now that few workers have had any practical experience with it. This lack of popularity is understandable to those who have attempted to use the gelatin injection techniques that are described in the texts on anatomical methods. These require melting the gelatin and warming the specimen, or, if "cold" or iodized gelatin is used, immersing the entire specimen in formalin to solidify the injection mass. Over a decade ago, Schlesingere described an ingenious modification of Tandler's cold or iodized gelatin mass that greatly simplified and expanded its use. Schlesinger demonstrated that if the gelatin solution were iodized sufficiently to be fluid at room temperature, and were buffered properly, formalin could be added directly to the mass just before injection; only after sufficient time had elapsed for good vascular penetration would the mass gel. Designed primarily for roentgenographic visualization of arteriosclerotic and thrombotic lesions of the coronary arteries, however, Schlesinger's mass has distinct limitations for other use. The extent of the injection is restricted to vessels larger than 50-100.& by the use of a large amount of barium sulfate for radiologic opacification. The water-soluble dyes he recommended for multicolored injections stain the tissues, and lose their color during bleaching, clearing, or preparation of the injected tissue as routine histological sections. The bacteriological gelatin which he recommended was designed for another purpose and has been found to vary greatly in the characteristics which are important in its use as an injection mass. In order to overcome these limitations we undertook analysis of certain properties of Schlesinger's basic mass, employing a new gelatin of constant character and using inert pigments of fine particle size instead of soluble dyes. Through this study we have evolved several simple formulae which yield injection masses suitable for a variety of purposes. In addition