No abstract

The significance of the observation by Staedeler and Frerichs (1858) of "colossale Quantitaten" of urea in the blood and tissues of some skates and a shark remained obscure for four decades. In 1897 Bottazzi reported that the freezing point depressions of elasmobranch blood and of sea water were approximately equal, that is, they had approximately the same total solute particle, or osmolal, concentrations. But whereas sodium and chloride make up the bulk of solute particles in sea water, Rodier (1899) observed that urea accounted for about one-third of the solute particles of elsamobranch blood. Rodier also noted that the freezing point depression of the fish blood was generally slightly greater than that of the animal's sea-water environment, an observation which has been re-

Thin slices of rat liver, kidney, and M. rectus femoris and thin, flat pieces of albumin-gelatin gels (which approximated the tissue slices in mass, dimensions and protein content) were immersed in formalin solutions at various concentrations, in some cases with variable amounts of NaCl (0.11-0.25M) added, and in some cases buffered at pH values ranging from 3.5-7.0. The slices were weighed at frequent intervals for the first 20 hours of immersion. Weight changes occurred rapidly. With the exception of the neutral buffered formalin curves, three families of response curves were obtained for the three tissues. With both formalin and formalinsaline solutions weight gain was inversely proportional to the solute concentration, but the formaldehyde particles apparently are not involved osmotically. The total osmotic concentration of formalin solutions, therefore, is not a factor in the swelling or shrinking of tissue slices. The presence of contaminants could be responsible for the effective osmotic concentration observed with these solutions. The weight response of slices is influenced by the pH of the formalin. Although the response of the gel system to any particular solution was quantitatively greater, it was qualitatively the same as the tissue slice response.

No abstract

A study was made of the weight changes undergone by slices of rat liver, kidney, and other organs immersed in certain fixatives containing chromium. In some experiments the data could be interpreted as indirect measurements of the fixative's ‘effective’ osmotic pressure, or ‘tonicity’, a property which usually differs from the fluid's ‘total’ osmotic pressure. In the case of kidney slices exposed to aqueous potassium dichromate, the rapidly occurring and reproducible responses seem proportional to the fixative concentration; no clear-cut differences were observed with liver slices similarly exposed. Altering the concentration of chromic acid did not affect quantitatively or qualitatively the response patterns of either tissue. Responses of slices to combinations of dichromate and formalin suggest cumulative action of the two moieties. The response patterns to the latter fluids could be modified by the addition of ‘indifferent’ substances such as sucrose.