FERMENTS 839 



dimples appear on the surface of the Loeffler medium. The greater the amount of 

 trypsin required to cause digestion, the higher the titer of antitrypsin in the blood. 

 By conducting a control series with the two normal pooled serums one may determine 

 whether in a given case the antitryptic power of the blood is normal, increased, or 

 decreased. 



(a) Does this test possess any practical value? 



(b) Discuss the presence of antitrypsin in the blood-serum. 



EXERCISE \ 9. FERMENTS (Continued) 



EXPERIMENT 51. ABDERHALDEN SEROENZYME REACTION IN PREG- 

 NANCY 



The technic of this test is very exact. The glassware should be 

 sterile and all manipulations carried out carefully and exactly as laid 

 down by Abderhalden. Consult the text for the technic (Chapter 



XV). 



1. Test five Schleichter and Schull shells No. 579a for permeability to albumin, 

 using 5 per cent, egg-albumen water and the biuret or ninhydrin reaction. 



2. Those shells which prove impermeable to albumin are now tested with a 1 

 per cent, solution of silk peptone (Hochst), using ninhydrin as the indicator. The 

 shells impermeable to albumin and permeable to peptone are suitable for the main 

 test. 



3. Secure a fresh human placenta; wash thoroughly to remove blood; cut into 

 pieces about the size of a dime; wash and rewash until perfectly white; search care- 

 fully for tiny blood-clots; boil repeatedly until the water reacts negatively to nin- 

 hydrin. Consult the text-book for the exact technic. Abderhalden lays a great 

 deal of stress upon the proper preparation of the substratum. 



4. Secure blood from a patient in advanced pregnancy; also a specimen from a 

 male. After a few hours, separate the serums and centrifuge thoroughly until free 

 of cells. The serums should not be over twelve hours old. 



5. Conduct a reaction after the technic given in the text-book, including the 

 controls. 



(a) Describe the biuret and ninhydrin reactions. 



(b) Why must the shells be so carefully tested? 



(c) Why must the placenta be free of blood and boiled previous to 

 the test? 



(d) Why should an aseptic technic be employed? 



(e) What are the prevailing views regarding the specificity of the 

 ferments? 



(f) Has the pregnancy test a practical value? 



(g) Give the principles of the optical method. 

 (h) Why is the serum control so important? 



(i) Enumerate the principal sources of error in the technic of the 

 dialysation method. 



