190 NOTES ON CETRARIA ISLANDICA 



Two rabbits, weighing 2.2 and 2.3 kilos respectively, were starved for six 

 days. The control animal (2.3 kilos) was killed and the glycogen content of 

 the liver found by the Briicke-Kiilz method to be 0.286 gram (0.7 per cent). 

 The other rabbit (2.2 kilos) received 10 grams of lichen in, suspended in 

 warm water, in five portions through the stomach sound at intervals of two 

 hours. Twelve hours after the last portion was fed the animal was killed. 

 The glycogen-content of the liver was found to be 0.086 gram (0.25 per cent). 

 Another rabbit of 2 kilos, likewise starved, was fed about 8 grams of 

 lichenin in several doses. The animal was accidentally killed immediately 

 after a portion had been fed. The liver did not contain a weighable amount 

 of glycogen. 



The writer has not succeeded in finding rabbits that would eat any con- 

 siderable quantity of the lichen itself, even after extraction with potassium 

 carbonate to remove the bitter taste. Further experiments with larger quan- 

 tities of lichenin are desirable. 



Isolichenin. This carbohydrate, to which is due the blue 

 iodine-reaction in the nitrates from the lichenin preparation, 

 has received little investigation.* It is in some respects 

 closely related to soluble starch. The amount present in the 

 lichen is decidedly less than the amount of lichenin, and a 

 micro-chemical study shows it to be distributed through the cell 

 walls of both the cortical and medullary portions of the plant. 

 Micro-chemical reactions for cellulose give negative results. 



Preparation. The nitrates from the lichenin were concen- 

 trated in vacuo at a low temperature (35-40C.). If any 

 remaining lichenin settled out on cooling it was filtered off 

 and the solution was treated with several volumes of alcohol. 

 The somewhat gummy precipitate was redissolved in hot 

 water and again cooled. Further traces of lichenin were re- 

 moved by filtration from the concentrated fluid ; the isoliche- 

 nin was reprecipitated with alcohol, extracted with alcohol 

 and ether, and reduced to an almost white powder, containing 

 0.4 per cent ash. This preparation dissolves with difficulty 

 in cold water, readily in hot water, from which it does not 

 separate on cooling. With iodine solution it gives a blue 

 coloration. 



Hydration by dilute acid. The following data were obtained 

 by the methods already indicated for lichenin : 



* Cf . Berg, loc. cit. ; Honig und St. Schubert, loc. cit 



