A Text-book of radiology

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 edition. Excerpt: ...as this not only increases the time necessary for fixing, but is more than likely to cause a discoloured and foggy negative. The subsequent operations of intensification or reduction if necessary, printing, mounting, and so on, differ in no way from those in ordinary photography, and the reader is referred to any one of the numerous pamphlets obtainable from dealers in photographic supplies for a few pence or perhaps gratis. These will give all information that may be required. Exposure.--This is iu all probability where the beginner's greatest difficulty arises, and it is none the more easy because it is impossible to give any fixed rules for his guidance. People vary as regards the size and thickness of their various parts, as well as in the opacity of their tissues. Strong athletic subjects are always more opaque to X-rays than others of similar weight and size. Also the X-ray tube is a more or less constantly varying quantity, as regards the quality and quantity of X-ray energy emitted; and further variations are likely to take place in the electrical circuit. With all these factors at variance, the impossibility of laying down any fixed rules is apparent. At the same time, if we take a standard size tube and work it at its critical current, which will be about one rnilliampere, at a standard distance of 24 inches from the plate, it will be found that the subjoined list of exposures will be found very fairly correct. Hand and toes...... 20 seconds. Forearm and arm...-30,, Shoulder 60 Thorax:. 60 Head........ 2 to 3 minutes. Abdomen........ 2 to 3,, Hip........... 2 minutes. Thigh......... 1 minute. Knee......... 1,, Leg............ 40 seconds. Ankle 30 In this simple exposure table it is assumed that the penetration of the tube is about 8 or...