THE VISCERAL ANATOMY OF THE GROUND-RAT. 225 
34. ON THE VISCERAL ANATOMY OF THE GROUND- 
RAT (AULACODUS SWINDERNIANUS).* 
Our knowledge of the visceral anatomy of the Rodents is still in so Page 786. 
incomplete a state, and the prevalent ideas on their classification so 
correspondingly vague, that until the details of the structure of the 
most important types have been published, it will be impossible to 
jadge of their-mutual affinities. 
I take the present opportunity of noting the most important points 
in the Ground-Rat (Aulacodus swindernianus) of West and South 
Africa, a male specimen having very recently died in the Society’s 
Gardens. ; 
The tongue is elongate and narrow, not divided into an anterior 
thin, and a posterior deeper portion, but of nearly uniform depth, 
blunt and rounded at the tip. Among the papille filiformes of its 
superior surface, papille fungiformes are scattered in small numbers. 
The circumvallate papille are represented by two long, narrow, elon- 
gate, circumyallate elevations, one on each side of the median line, 
_ where they nearly meet, running forwards as they diverge to form a 
~ ¥. The root of the tongue is covered by large, lax, and scattered 
conical papille between those last described and the hyoid bone; 
farther back it is smooth. 
The salivary glands present no peculiarities ; the submaxillary are 
the largest. 
The esophagus, after perforating the diaphragm, runs for half an 
inch or more in the abdominal cavity before it joins the stomach; its 
epithelium, in the inverted stomach, projects beyond the cardiac orifice 
as a stiff puckered tube for about one-eighth of an inch. 
The stomach is simple, proportionately slightly longer than in man, 
with the pyloric cul-de-sac also a little more developed. Its mucous 
membrane is smooth, except near the pyloric end, where there are a 
few irregular rugs. No ridges of mucous membrane run along the Page 757. 
lesser curvature from the cardiac to the pyloric orifice. The pylorus 
is large. 
In the duodenum the pyloric extremity is much dilated pyriformly 
as in many Rodents. The mucous membrane becomes velvety, with 
villi on the duodenal surface of the pyloric valve, and continues so 
along the small intestine. The whole small intestine is 54 feet long. 
—. | 
pre 
* “Proceedings of the Zoological Society,” 1873, pp. 786-789. Read, Dec. 2, 
1873. 
Q 
ET 
