Further Observations of the Effects of X Rays upon Lymphocytes

Reprinted from The Journal of Pathology and Bacteriology, Vol. XXIII. (1920). IN a previous paper (1919) we have shown that the lymphocytes in the circulating blood of the rat are extremely vulnerable to small doses of X rays. These cells may be even more delicate indicators to X rays than is an ordinary X-ray plate, as the following experiment shows. A rat, the blood count of which had been taken, was exposed to X rays for τν second ; one hour later a blood count showed a reduction of 20 per cent, in the number of lymphocytes ; an X-ray plate was then placed in the position previously occupied by the rat and a similar exposure given ; the plate on development showed no visible photographic action. This experiment has been repeated. The lymphocyte shows the selective action of X rays to a striking degree ; the term indicates that, if the same intensity of X rays be directed on to different varieties of cells, then the reaction of each variety of cells will be specific. A very small dose of X rays, which gives rise to a marked alteration in the number of the circulating lymphocytes, has no other recognisable effect upon the animal. In this paper the dose of X rays will be referred to in terms of time of exposure ; the quantitative data will be found in paper, loc. ait.