136 The Ottawa Naturalist. [September 



acids. With phenolphtalein the reaction was invariably acid all the 

 way, whilst it was alkaline to methyl orang-e, thus showing- that 

 the acid reaction was due to a very weak organic acid 

 probably to dissolved acids set free from fats. The alkaline 

 reaction indicated by methyl orange can only be due to weak 

 organic acids combined with alkalies i.e. in all probability to dis- 

 solved soaps. Such a weak acid would not decompose the soap, 

 and so the objection to the theory falls to the ground. 



Another objection is that the amount of the alkali required 

 for the saponification would simply be enormous. Munk reckons 

 that to so combine with the fatty acids of 200 grammes of fat 

 about 40 grammes of sodium carbonate would be required. Now 

 a dog weighing 25 kilogrammes can easily digest from 200 to 350 

 grammes of fat in twenty-four hours. Supposing only 200 

 grammes are digested and that all this is absorbed as soap and 

 glycerine, about 40 grammes of sodium carbonate will be required 

 for the purpose ; now the total blood only contains, in such an 

 animal, alkali equivalent to 6 grammes of Nag CO3. If the other 

 fluids of the body be supposed to contain an amount of alkali 

 equivalent to another 6 grammes, the total alkalinity is equal to 

 12 g-rammes of Nag CO3. 



In this objection Munk loses sight of the fact that during the 

 process of absorption of fat as soap and glycerine and its subse- 

 quent synthesis in the epithelial cells, the alkali combined in the 

 first portions of the soap absorbed is again set free immediately 

 after absorption, and what is to prevent that alkali from being, in 

 some way, in the natural course of circulation, brought back to the 

 intestine there to unite again with some more fatty acid to form 

 soap and thus keep up the continuous action of composition and 

 decomposition ! 



Whatever may take place the consensus of opinion seems in 

 favour of the theory that fats are absorbed as soaps and glycerine 

 and reformed by synthesis in the epithelial cells and then deposited 

 in the cells of the adipose tissue. 



Another problem about fat which has puzzled many a physiolo- 

 gist is its origin. From which class of food compounds is fat 

 derived ? 



