456 BUMP US. [Vor. XII. 
VIII. Are variations more frequent in males than in 
females ? 
IX. Are there anatomical grounds for the theory of verte- 
bral intercalation ? 
METHODS. 
Until within a few months the examination of a large series 
of skeletons involved the expenditure of considerable time for 
their proper preparation, the destruction of valuable anatomical 
material, the occasional loss of certain cartilages, and the too 
frequent misplacement of disjointed parts. The truly wonder- 
ful discovery of Rontgen, however, has placed in the hands of 
the anatomist an economical means for the most critical exam- 
ination of the bones, zz sztu, without the use of macerating 
fluids or the scalpel, and a means readily applicable, without 
injury to the most valuable museum specimen or even to the 
living animal. 
The one hundred alcoholic specimens on the comparative 
examination of which this paper is based, belong to the 
museums of Brown University and the Boston Society of 
Natural History. Each animal, properly numbered, was bound 
in a proper position to a thin piece of board, and the board with 
the specimen attached was then placed upon an envelope of 
black paper containing a common photographic plate. When 
large plates were used as many as ten animals were exposed at 
the same time. 
Immediately over the table on which lay the photographic 
plate, and approximately 500 mm. distant, was suspended a 
Crooke’s tube of the Elihu Thomson pattern, rendered fluores- 
cent by means of a Tesla coil. The exposure was invariably 
five minutes. When the tube became dim it was warmed with 
a Bunsen flame until the return of the brighter illumination. 
The plates were developed with the ordinary “‘ pyro” developer. 
The negatives, taken so as to show both the dorsal and 
lateral views of the vertebral column, were so clear that the 
ultimate joints of the tail could be readily counted. The 
amphiccelous structure of the vertebra and the minute pores 
of the bones were often exhibited with remarkable detail. A 
