BIOCHEMICAL REACTIONS 159 



serum alone and placenta alone. Great care must also 

 be exercised to see that all bacteria are excluded, and 

 that the membranes are not permeable to protein, but 

 will allow peptone to pass through. If the shells are 

 used repeatedly, they must be scrupulously cleansed 

 in order to avoid contamination from previous tests. 

 By carrying out all proper precautions, the great ma- 

 jority of observers have obtained results agreeing with 

 those of Abderhalden, the test proving positive in pa- 

 tients ranging from the early weeks of intra- or extra- 

 uterine pregnancy to a few weeks post partum. 

 Pearce and Williams {Surgery, Gynecology , and Ob- 

 stetrics, April, 1913, p. 411) report a series of 36 cases 

 of pregnancy giving positive results, controlled by 

 negative results in a male and a non-pregnant female. 

 Insufficient work has as yet been done using normal 

 serum and serum of persons suffering with various 

 diseases, to place the test on a conclusive basis. Pearce 

 and Williams (loc, cit.) tested the reaction of serum of 

 pregnant women with various organs, such as kidney, 

 liver, and uterus, instead of placenta, and obtained 

 positive results in some cases. While the test gives 

 promise of becoming of importance in the diagnosis of 

 pregnancy, yet further experiments to eliminate pos- 

 sible sources of error must be carried on before it will 

 attain wide clinical application. In view of the pres- 

 ent possible sources of error in the reaction, and par- 



