It may seem paradoxical that in a disease process seemingly so well defined and meticulously studied through these many decades as tuberculosis, a review such as that of Wells and Long would present a picture of absolute fluidity, of constantly changing views.
While paradoxical, it is nevertheless extremely hopeful. The tremendous activity in tuberculosis research which necessitates such constant revision is particularly apparent when one compares the second with the first edition of the review under consideration, and we may take considerable pride in the fact that American investigators have themselves contributed much to the newer information that is summarized in the book of Wells and Long.
Particularly the first chapters have been subjected to thorough revision so that they present a most complete review of the knowledge that has developed. There is no material expansion in the length of this portion of the book, because obsolete material has been