96 R H. A. PLIMMER. 



the determination is carried out all proteids and allied bodies must be 

 separated from the solution. For this purpose I have used mercuric 

 nitrate as employed by Bierry. The method of boiling after acidification 

 employed by Bainbridge is inadequate since it only removes the greater 

 part of the coagulable proteid, leaving the proteoses and other disinte- 

 gration products still in the solution. Since my object is merely to 

 determine the presence or absence of lactase in the given juice or tissue 

 extract, I have always allowed ample time for the action of the ferment 

 to take place, generally leaving the solutions in the incubator for two 

 or three days. In every case two experiments have been made side by 

 side, one consisting of the mixture of the juice or extract with lactose, 

 and the other consisting of exactly the same amounts of lactose and of 

 boiled juice or extract. Both these solutions have been subjected 

 throughout to exactly the same procedure. Finally, in each case the 

 osazones have been made and the glucosazone, if present, separated 

 from the lactosazone, and the identity of these substances determined 

 both by the melting point as well as by an estimation of their content 

 in nitrogen by Dumas' process. By adopting these methods it is easy 

 to detect the presence of a lactose-splitting ferment. In every case, 

 when such a ferment is present, we can after one to three days' incuba- 

 tion get a big difference in the copper reducing power of the two 

 solutions as well as definite production of glucosazone. In every case 

 I have also taken polarimeter readings of the two fluids. This method, 

 however, is much less delicate than the other two, and suffers moreover 

 from the drawback that it is impossible to separate ammo-acids from the 

 solutions, so that the final rotatory power of the solutions may differ 

 apart from any difference in their sugar content. 



I have investigated the question of the presence of lactase after 

 feeding with milk and milk sugar in five animals, namely 4 dogs and 1 

 kitten. The dogs were fed with meat and biscuit and in addition about 

 two pints of milk and two ounces of milk sugar per diem. This diet was 

 continued from two to five weeks. At the end of this period the animals 

 were anaesthetised, and pancreatic juice, excited by injection of secretin, 

 was collected by Prof. Starling for a period of 4 to 6 hours. The 

 animals were then killed, the pancreas cut out and pounded up with sand. 

 The pounded organ was then suspended in toluol water until the next 

 day, when it was centrifuged, and the opalescent supernatant fluid taken 

 and handed to me to determine the presence or absence of lactase. In 

 each case the pancreatic juice and the pancreas infusion were divided 

 into two parts ; one part was kept at 100 C. for 20 to 30 minutes in 



