The Visceral Anatomy of the Kangaroo Rat

Abstract

kangaroo rat (Dipodomys) is a mammal of particular interest. An investigation of its visceral anatomy was undertaken by the writer with the purpose of describing in detail the internal anatomy of this genus and of making comparisons with other rodents. In the drawings presented the organs are shown both in situ and removed from the body. size and weight of the various organs are of little importance in a topographical study. data presented are intended to give an idea of the comparative size and weight of each organ with respect to other organs of the same specimen. For purposes of orientation and comparison, considerable use was made of Greene's Anatomy of the Rat (1935), which is a study of the albino rat. The thoracic and abdominal viscera of primates (Straus, 1936) was used as a model for the investigation. This work was carried on under the guidance of Dr. W. W. Newby and Professor Stephen D. Durrant, both of the University of Utah, and to them I am deeply indebted. Appreciation is acknowledged to Dr. R. V. Chamberlin, head of the Biology Department at the University of Utah, for supplying facilities necessary in completing this work. Materials and methods.-Several specimens of D. microps levipes were obtained for me by Dr. Newby and Professor Durrant at Pine Valley, 50 miles west of Milford, Millard County, Utah, at 5000 feet altitude. These were preserved in formaldehyde. A second lot of specimens, of D. ordii columbianus, was trapped by me on the sand dunes west of Salt Lake City, 1 mile east of Great Salt Lake, at 4200 feet altitude. They were placed immediately in the embalming fluid suggested by Hyman (1922). drawings and descriptions presented are representative of the majority of the specimens. slight variations observed were probably due to differences in methods of preservation and not to species differences. It is beyond the scope of this investigation to determine the variations in the visceral anatomy of the two species. conditions herein stated are considered as general for the genus Dipodomys. External morphology.-There is a combination of external characteristics which sets the kangaroo rat apart from all other rodents: hind legs are over three times as long as the weaker front legs; the paintbrush tail is longer than the body; the external cheek pouches are characteristic only of this family (Heteromyidae) and the pocket gophers (Geomyidae); the head is broad, flattened and triangular, carrying large, protruding eyes and ears of moderate size.