Plasma hemoglobin determination in beagle dogs. An adaptation of the method of Crosby and Furth

The plasma hemoglobin concentration of beagle dogs was measured following an improved bleeding technic which minimized trauma of the red cells. The benzidine reaction (benzidine dihydrochloride) was used to measure the hemoglobin present. Plasma hemoglobin values of the first 2 ml of blood collected were statistically significantly higher (P less than 0.01) than values of the next 2-3 ml of blood. Plasma hemoglobin values of normal beagles were 0.5-2.5 mg/dl in minimally hemolyzed samples. Recovery rates of up to 92% of hemoglobin added to plasma were possible with this method.

The Perception of Three-Dimensional Solids

Arising from the discussion of differences between three- and two-dimensional perceptual objects in relation to current theories, an attempt is made to extend the traditional type of shape-constancy investigation into the realm of three-dimensional solids. For this purpose a specially constructed “solid” is made to undergo progressive physical changes of shape while being compared, under controlled conditions, with various stationary two-dimensional projections.

The results indicate that three-dimensional solids possess perceptual properties not shared by simple surfaces or representational projections. It is suggested that changes in the magnitude and sign of the constant errors obtained under certain conditions can be explained only on the assumption that subjects react to the stimulus in terms of some conceptual schema, or reference frame, involving mental processes other than those of perception.

The Role of Spatial Stimuli in the Perception of Shape.: Part II

Subsequent to the experiment described in Part I, the röle of spatial-surround cues is further investigated by attempting to modify the character of the environment. Pairs of shapes are matched, both stationary and rotating, within an Ames-type equivalent space. These shapes are of two kinds. The first is calculated for normal perceptual space, and the second pair are comparable only in the equivalent space. Comparison of matchings indicates that the perceived shape is a product of interaction between cues emanating from the object and the surround, in terms of which the object cues are evaluated, though the concept of “anchorage” or “reference frame” is distinguished from suggestions advanced by some authors.

The Role of Spatial Stimuli in the Perception of Shape.: Part I

Arising from earlier studies of shape constancy (Langdon, 1951; 1953) an attempt is made to examine the rôle of spatial-surround cues in shape perception, as distinct from cues provided by the object. A series of shapes is compared in total darkness, firstly with shapes stationary and secondly with shapes rotating continuously. The findings are compared with those obtained in normal illuminated surrounds. The results indicate that surround cues play an important part in perception of orientation, and hence perception of shape. An explanation is suggested involving the use of surround cues as “anchorage” or “reference” frames. This is investigated further in Part II of this paper by an attempt to modify the character of the surround cues in a controlled way.