Page:Defensive Ferments of the Animal Organism (3rd edition).djvu/221

 evaporates unevenly in the incubator. Take, for instance, Cases 6 and 8. In both cases the serum alone nearly reaches the limit, 1. Then, should the dialysate, in the experiment organ + serum, evaporate more strongly, or should the corresponding dialysate become more strongly concentrated, during boiling, than that of the relative control experiment, then we shall get a positive reaction owing, entirely, to the concentration; in which case we shall get a wrong result. These examples may be a warning to those who make use of a particular technique in an imperfect manner.

It is easy to understand that errors in diagnosis have often occurred, and that, on the other hand, brilliant results have been reported.

As a matter of fact our limit value, 1, is seldom attained. Unfortunately, this occurs just when carcinoma, myoma, salpingitis, exudates, suppurations, or hæmorrhages are present, that is, just when the method should diagnostically give the most valuable differential results. It is obvious that the investigation of such cases requires double care.

The performance, under absolutely equal conditions, of a particular experiment, and its control, is of decisive importance in regard to the results obtained. In the first place, absolutely pure distilled water must be used. Water, which gives an acid or alkaline reaction, leads inevitably to erroneous results. Ninhydrin