158 APPLIED IMMUNOLOGY 



method is as follows: Fresh placenta is cut in small 

 pieces and repeatedly boiled with a little acetic acid 

 until all soluble protein is removed. This is deter- 

 mined by testing with the biuret reaction. The pa- 

 tient's serum is collected by puncturing a vein at the 

 elbow. Five or six c.c. of serum should be obtained, 

 and must be absolutely free from haemoglobin. For 

 dialysis, Schleicher and Schull's diffusion shells are 

 employed. These membranes must be impermeable 

 to the protein of blood-serum and permeable to pep- 

 tone, as ascertained by preliminary tests. The ninhy- 

 drin reaction is used for reading the results. This 

 substance, the full name of which is triketohydrinden- 

 hydrat, gives a blue color with the end products of 

 protein digestion. 



Into one of the diffusion shells are placed 1 

 gramme of the boiled placental material and 1.5 to 2 

 c.c. of patient's serum. The membrane is then placed 

 in a small beaker containing 20 c.c. of water. The 

 fluid in and outside the membrane is then covered 

 with toluol and the whole incubated at 37° C. for 16 

 to 24} hours. At the end of this time, the water in the 

 beaker is tested for products of proteid digestion by 

 adding to it 0.2 c.c. of a 1 per cent, watery solution of 

 ninhydrin. If the reaction is positive a blue color re- 

 sults. The reaction must be carefully controlled by 

 using at the same time other membranes containing 



