With the development by Dr. Coolidge of the self-rectifying roentgen-ray tube and the portable transformer, and the subsequent production of large numbers of these completed units, a long felt want has been realized.
Designed especially as a portable unit for bedside use in hospitals, they are nevertheless capable of handling a large part of the work that comes to the general practitioner. This fact, together with the low cost, ease of installation, and simplicity of operation, will mean that many of these units will soon be in the hands of the profession.
There is, however, one very important feature which until now the designers have apparently overlooked, and that is a means for shifting the tube for stereoscopic plates. The man accustomed to stereoscopy will feel this loss keenly, and the physician who has not yet learned to use stereoscopic roentgenography in his roentgenographic examinations should know that the difference