The difficulties encountered in making a diagnosis of a suspected primary lesion are well known. The use of a dark ground illuminator is sufficient evidence that the proper staining of the Spirochaeta pallida by the various methods described in standard books on pathologic technic is not an easy task.
Thus, Mallory and Wright1 give not less than four methods of staining, besides Burri's india ink method. Every one of the methods referred to is fairly difficult, making it impossible for men with no special laboratory training to obtain proper results. In fact, in this laboratory, employing Wright's method as described by Mallory and Wright, we have tried time and again to stain smears of cases in which numerous spirochetes were found with the dark ground illuminator, but with no success. Of course, that does not condemn the method; but it at least shows that it does not work in