THE SPLENIC MICROVASCULATURE OF THE RED-EARED TURTLE (CHRYSEMYS-SCRIPTA-ELEGANS) - A STUDY CONCERNING THE QUESTION WHETHER THE CIRCULATION IS ANATOMICALLY OPEN OR CLOSED

The splenic microvasculature of the turtle Chrysemys scripta elegans w as studied by means of scanning electron microscopy of vascular corros ion casts and critical point dried tissue. In addition light- and tran smission electron microscopic investigations were carried out. Within the organ the arteries are surrounded by periarterial lymphoid sheaths . The majority of the arterial capillaries, which emerge from these ce ntral arteries have open endings within the reticular meshwork of the red pulp. Approximately 10% of the capillaries directly connect with t he venous origins. Since these venous capillaries of C. scripta elegan s resemble those of nonsinusal mammalian spleens we termed them pulp v enules. Several blood cells were seen in passage through the fenestrae of the pulpvenules. The blood cells overcome these wall pores either unimpeded or a striking deformation of the passing cell occurs. In the subcapsular region of the organ radially arranged venous vessels are observed, which drain into a collecting vein.